If you run a small engineering or architectural firm, you probably have a folder somewhere on a network drive that everyone calls “the archive.” It holds ten, twenty, sometimes thirty years of DWG and DXF files. And every few weeks, the same thing happens: someone needs to find a specific drawing from 2014, no one remembers the exact filename, and an hour disappears while a designer opens files one by one in AutoCAD trying to recognize them.

The cost of this shows up as billable hours lost to file-by-file searches, wrong revisions attached to client proposals, and tribal knowledge that walks out the door with departing employees. The drawings themselves are valuable assets — years of paid work and reusable detail libraries. Treating them as an opaque pile of files wastes that value every day.

The solution is conceptually simple. Generate a preview image for every CAD file in the archive. Display those previews in Windows Explorer, on an intranet page, or inside a document management system. Suddenly the archive is searchable by eye, and finding old work takes seconds instead of an hour. The hard part is doing it in batch, without buying an AutoCAD license for every employee who might need to look at a drawing.

Why generating DWG previews is harder than it looks

If preview generation is so useful, why doesn’t every firm already have it? Because the obvious solutions all have problems that only become visible after you try them.

The AutoCAD licensing problem

AutoCAD itself can generate thumbnails and previews. So can AutoCAD LT. But an AutoCAD LT subscription runs around 500 USD per seat per year, and that’s only for viewing and basic editing. If only your designers need to actually edit drawings, but five other people in the office occasionally need to look at them, you’re either buying licenses you don’t really need, or those five people keep interrupting the designers.

Autodesk does offer DWG TrueView as a free viewer, and it does add Windows Explorer thumbnails on machines where it’s installed. For a single user this is fine. For automated batch processing across a 40,000-file archive, building previews for a web portal or DMS, or generating previews on a server with no GUI session, it’s the wrong tool.

Why online viewers are off the table for most firms

Cloud CAD viewers such as Autodesk Viewer or DWG FastView are useful for collaboration and file sharing, but they are less practical for large legacy archives.

Many engineering firms cannot freely upload client drawings due to NDAs, internal policies, or industry regulations. In addition, most cloud viewers are designed for opening individual files rather than batch-processing tens of thousands of drawings into a searchable preview library.

For archive management, local batch preview generation is often simpler and easier to maintain.

The “just write a script” trap

The third path most firms consider is writing a script using the AutoCAD .NET API, ODA libraries, or a Python toolchain. This works if you have a developer. Most small firms don’t, and custom scripts tend to break silently when DWG versions change or when someone upgrades the server. Six months later no one remembers how the script works, and the preview pipeline quietly stops producing anything for new files.

What you actually need from a CAD preview workflow

Before picking a tool, it helps to make the requirements explicit. A workable batch CAD preview system for a small firm needs to:

1. Process files in batch, ideally thousands at a time, without manual clicking
2. Run on a standard Windows machine without requiring AutoCAD installation
3. Support DWG, DXF, and ideally older or related formats like DWF, HPGL, and PLT for legacy archives
4. Output common image formats (PNG, JPG) for thumbnails, plus PDF for sharing and SVG for high-quality web previews that scale on screen
5. Automate itself — watch a folder, process new files as they arrive, no scheduled human intervention
6. Handle errors gracefully so one bad file doesn’t stop the whole batch
7. Stay on premises, with files never leaving the company network

This list also functions as a buying checklist. Any tool that can’t tick most of these boxes isn’t really solving the problem; it’s just shifting work around.

How reaConverter handles batch CAD preview generation

reaConverter is a Windows batch file conversion tool that has been developed for over twenty years. It supports more than 800 input and output formats, including the CAD formats that matter for archive work: DWG, DXF, DWF, HPGL, PLT, and several others. For the use case described here, the Pro edition is what you need, because batch automation and watched folders are Pro features.

Download reaConverter Pro

Supported input and output formats

On the input side, reaConverter reads DWG and DXF files from AutoCAD versions going back to early releases, plus DWF, HPGL/2, PLT, and other 2D CAD formats commonly found in legacy archives. This matters more than it sounds. Most archives accumulate files from different CAD tools over the years, and a preview system that only handles current AutoCAD versions leaves a chunk of the archive invisible.

On the output side, you can generate previews in any image format reaConverter supports. For a typical preview workflow, three outputs cover almost everything:

• PNG or JPG thumbnails for Windows Explorer, file managers, and most document management systems
• SVG for web-based preview interfaces where users may want to zoom into the drawing
• PDF for archival and sharing with clients who don’t have CAD software

You can output more than one format from a single conversion job. A common setup generates a small JPG thumbnail and a larger PDF for every DWG, both saved alongside the original.

Automating the workflow

This is where reaConverter Pro earns its keep. There are two automation modes that matter for archive work.

Watched folders monitor a directory continuously. When a new DWG file lands in the folder, reaConverter processes it automatically using a saved conversion profile and writes the output wherever you’ve configured. For an active project archive where designers save new drawings throughout the day, a watched folder means previews appear within seconds of a file being saved, with no scheduled jobs and no human involvement.

Command-line operation runs reaConverter as a CLI tool. This is what you want for the initial bulk conversion of an existing archive, and for any workflow that fits better into Windows Task Scheduler or a server-side script. A nightly job that processes the day’s additions, or a one-off command that converts the entire historical archive over a weekend, both work cleanly from the command line.

Together these two modes cover the realistic shape of an archive: a large historical backlog that needs a one-time bulk conversion, plus a continuous stream of new files that need previews generated as they arrive.

Adding OCR for scanned legacy drawings

There’s a bonus use case worth mentioning, because almost every firm older than fifteen years has it. Somewhere in the archive there are scanned PDFs and TIFFs of paper drawings from the pre-CAD era, or from acquired companies, or from projects where the originals were lost. These files are technically in the archive, but they’re functionally invisible — you can’t search their contents, and visual thumbnails of scanned blueprints often look identical to each other.

reaConverter includes OCR. You can batch-process scanned drawings to extract the text — title blocks, revision tables, notes — and either embed it back into a searchable PDF or output it as a text file alongside the original. Combined with preview generation, this turns a pile of opaque scans into searchable, browsable assets. It’s the same workflow as the DWG preview pipeline, just with a different input type.

Where this approach fits, and where it doesn’t

Honest limitations matter here. A preview system that promises to handle everything will disappoint at the worst possible moment.

reaConverter works well for:

• 2D architectural and engineering drawings (the bulk of most firms’ archives)
• Standard mechanical part drawings and assembly views
• Civil, structural, and electrical drawings
• Mixed archives with multiple CAD formats and legacy scanned documents
• Throughput in the thousands to tens of thousands of files

reaConverter is not the right tool for:

• Very large 3D assemblies — full automotive models, complex aerospace assemblies, large BIM coordination models with millions of polygons. These need a dedicated CAD or visualization platform.
• Drawings that depend heavily on custom AutoCAD object enablers (AutoCAD Architecture, Civil 3D, Plant 3D specialty objects may render in simplified form)
• Drawings with broken or missing xrefs — these will preview, but the preview will be missing the xref content, same as in any non-AutoCAD tool

If your archive is mostly 2D drawings with the occasional 3D model, reaConverter handles the realistic 90% case. If your work is large 3D assemblies, this isn’t the right tool, and that’s worth knowing before you invest setup time.

A practical setup for a 50,000-file CAD archive

Here’s a concrete recipe for a small firm with a multi-year archive that needs preview generation set up in an afternoon.

Step 1: Install reaConverter Pro on a single machine. This can be an existing workstation that’s left on overnight, or a small server. No special hardware is needed for 2D CAD work.

Step 2: Create a conversion profile. Open reaConverter, add a sample DWG file from your archive, and configure the output: typically a 1024×768 JPG thumbnail and a PDF. Save this as a named profile (for example, archive_preview). The profile captures every setting, so subsequent runs are reproducible.

Step 3: Run the initial bulk conversion. Point reaConverter at the root of your archive and let it process everything once. For a 50,000-file archive of typical 2D drawings, plan for this to run overnight or across a weekend depending on the machine. Use the command-line mode if you want to script it or run it on a server.

Typical performance on a mid-range Intel i7 workstation:

• ~3–5 standard 2D DWG previews per second
• ~8–10 hours for a 50,000-file archive
• Typical PNG preview size: ~100–150 KB per drawing

Step 4: Set up a watched folder for ongoing files. Once the historical archive is converted, configure a watched folder on the directory where new drawings are saved. From this point forward, every new DWG that designers save gets a preview generated automatically.

Step 5: Make the previews discoverable. This is where preview output meets your existing infrastructure. The simplest setup just stores PNG thumbnails in a parallel folder structure mirroring the archive, which Windows Explorer can browse directly. More ambitious setups feed the previews into a document management system, an intranet page built on a simple file index, or a tool like Daminion that’s designed for visual file libraries.

The result, after one afternoon of setup and one weekend of bulk processing, is that the whole archive becomes browsable by eye, and stays that way without further intervention.

Frequently asked questions

Does reaConverter require AutoCAD to be installed?

No. reaConverter reads DWG and DXF files natively and does not require AutoCAD, DWG TrueView, or any other Autodesk software to be present.

What CAD formats can reaConverter generate previews from?

The main supported inputs for CAD preview work are DWG, DXF, DWF, HPGL/2, and PLT. The full format list is broader, but those are the ones that matter for typical engineering and architectural archives.

Can reaConverter generate SVG previews of DWG files?

Yes. SVG is among the supported output formats, which makes it useful for web-based preview interfaces where users may want to zoom into the drawing without losing quality.

How does Watch Folder automation actually work?

You configure a folder for reaConverter Pro to monitor. When a file matching your filter appears in that folder, reaConverter applies the conversion profile you’ve assigned and writes the output to the configured destination. The whole process runs in the background and does not require a user to be logged in interactively, depending on how it’s set up to run.

Is there a licensing limit on how many files can be processed?

No. A reaConverter Pro license is a one-time purchase that allows unlimited file processing on the licensed machine. There are no per-file or per-batch fees.

reaConverter Pro is available as a one-time purchase Windows license. For firms maintaining large legacy archives, the time savings are usually immediate.

Download reaConverter Pro

If you are planning to print a graphics file on a plotting device, then converting it to PLT is the best option. Whether you are using a cutting plotter, a pen plotter or some other similar machine, the PLT format will ensure what you create on screen will match what you see in print.

PLTs are vector files that use the HPGL language and can be sent directly to print on a plotter. Such devices are often used for large-scale graphics such as maps, detailed plans or diagrams, posters and many more. The PLT format was originally created for Hewlett-Packard printers only, but in time became an actual standard in the industry. PLTs are currently compatible with most brands of plotting machines.

Install reaConverter

How does it work?

Load one or more image files you want to convert to PLT. They can be of any vector format or they can actually be PLTs as well — in which case reaConverter will function as a handy image editor.

Files can be dropped directly into the software’s main window, or picked manually from a local folder. In case you need to handle batch conversion, you can also add entire folders or use the Advance file select option and automatically pick a number of files according to their size or extension.

PLT saving settings

Go to the Menu button and click Saving settings → Format saving settings, and then click on the PLT tab.

In this window you can opt for rotating the PLT images 90 degrees to the left or to the right. Since PLT is a vector format, this option works differently than when applied to raster images. To be more precise, it means all vector coordinates of all points will be rotated.

Save the result

In the Saving settings tab, enter the location of the output files. Last but not least, make sure the PLT button is clicked in the Convert to section.

Then simply press Start!

Command-line interface

This handy feature that allows you to rotate vector PLTs during conversion can be processed both from reaConverter’s GUI interface and from command line, using this code line:

-plt_rotate = 0 - Do not rotate, 1 - Rotate 90 degrees right, 2 - Rotate 90 degrees left

Video Tutorial

Advanced users can rotate PLT files from command line interface or using DLL in manual, automated or scheduled mode. You are welcome to contact our technical support when you have any questions about reaConverter.

The PLT (Plotter) format is the best option when you plan to print maps, detailed building plans, banners, large posters or other types of line and curve drawings in full-color. Initially launched by Hewlett Packard for its own plotter printers, the PLT extension has now become an actual standard for almost all brands of cutting plotters.

PLT files can be created using AutoCAD and a few other types of computer-aided design software, or through conversion. They contain vector images which maintain their quality when scaled to different sizes and use the HPGL language. The main advantage of PLTs over PDFs, for example, is that they are designed particularly for plotter printers, which means you can send the large-scale graphics file directly to print.

From screen to print, however, minor errors can sometimes occur. One of the most frequent ones is represented by duplicated lines. Converting image formats to PLT can be done in no more than a few clicks with reaConverter’s latest edition. Plus, this powerful software also allows you to optimize the output file by correcting aspects such as duplicated lines, it makes printing process dramatically more efficient.

Install reaConverter

How to optimize PLT?

Load the file you intend to convert to PLT. reaConverter also supports batch conversion, so feel free to drop into its main window all files that need conversion.

You can also add entire folders, or files selected according to their extension and size, by clicking Advanced file select.

PLT saving settings

Go to the Menu button and click Saving settings – Format saving settings

In the newly opened window, go to the PLT tab and tick on the box near Remove duplicated lines.

This window can also be reached via a handy shortcut placed on the PLT button, from the Convert to section, in the lower part of the screen. In case you don’t see that button there, click Plus and get a full view of all output formats supported by reaConverter. Select PLT and once the button appears at the bottom of the main window, place the pointer on its upper left corner and click the Settings icon there.

Save your result

In the Saving options tab, opt for saving the output PLTs in a local folder of your choice or directly online. reaConverter offers here a lot of time-saving options, such as selecting directly the source folder or a subfolder as output destinations, and using a cloud storage service.

Finally, make sure you checked PLT as the extension for the output files, in the Convert to section, and simply click Start!

Command-line Interface

Converting files to PLT with the possibility of removing duplicate lines is also available with command line using cons_rcp.exe this code line:
-plt_remove_dup = 1 if you want to remove duplicated lines and = 0 otherwise

Video Tutorial

Advanced users can optimize PLT files with command line tool or DLL in manual, automated or scheduled mode. You are welcome to contact our technical support when you have any questions about reaConverter.

PLT is an image format associated with plotters — a type of printing devices that use vector graphics as input files, as opposed to regular printers, which can only print raster images. Plotters can be of different kinds, including pen plotters — printing devices using a pen to draw lines and curves on paper, and cutting plotters — using knives to cut shapes into paper or other types of materials.

Files with the PLT extension usually store maps, posters, detailed designs of machines and other types of monochrome or full-colored graphics. PLTs can be created using computer-aided design software, such as AutoCAD and Adobe Illustrator. Or they can be obtained via conversion from other image formats. The main advantage of PLT over other graphics extensions is that the image can be sent directly to the plotting device.

reaConverter’s latest release helps users manage batch conversion to PLT while also supporting output file optimization features, such as setting pen width. The latter can be done using plotter units (1 mm = 40 plotter units), using the software’s GUI interface or via command-line. Setting pen width offers better control over how the output file will look like and helps users make sure the image design will stay the same from screen to print.

Install reaConverter

How does it work?

Load one or more files that need to be converted to PLT.

Drag-and-drop them from an opened folder, add entire folders or use the Advanced file select option and automatically pick a group of files according to their extension or file size.

How to set pen width?

Click the Menu button and then go to Saving settings → Format saving settings

Here check the PLT tab and tick the box near Set pen width to

Insert the desired number of plotting units, while keeping in mind that 1 mm equals 40 plotter units. In this window you can also opt for other ways to optimize the output PLT images, including the removal of duplicated lines or rotation of the PLT image.

If you want to edit images before conversion

Optionally, check the Edit images tab, where you can find a real-time Preview box, offering you a glimpse of how the output image will look like.

In this section you can choose one of the many editing actions available, such as cropping, changing canvas size or adding watermarks.

Convert to PLT

In the Saving options tab, choose the folder where the output PLTs will be stored. It can be the same as the source folder, a subfolder or another folder of your choice.

Finally, don’t forget to click the PLT button in the Convert to section, from the lower part of the window. In case it isn’t there, find it by clicking the + Plus button.

Once it appears on the main window, you can place the pointer over it and click the Settings icon from its upper left corner, thus finding a shortcut to the window described above on this list (Format saving settings → PLT).

Finally, press Start and your newly converted PLTs will soon be ready!

Command-line Interface

Converting files to PLT with the possibility of setting customized pen width is not just supported by reaConverter’s GUI interface, but can also be processed via command line using cons_rcp.exe this code line:
-plt_pw = pen width in plotter units (1 mm = 40 plotter units)

Video Tutorial

You are welcome to contact our technical support when you have any questions about reaConverter.

Printing detailed maps, building projects or various types of full-colored graphics often works better when done via PLT than PDF files. As opposed to other comparable formats, PLT or “plotter” images are specifically designed for being printed with cutting plotters or other similar plotting devices. PLTs employ the HPGL language and can be created with several kinds of CAD software, such as AutoCAD, or through conversion. In case you have a PDF you intend to print with a plotter, reaConverter helps you handle the conversion quickly and effectively.

The main advantage of printing with a plotting machine — compared to laser-jet or inkjet printers — is that the former can use vectors as input files. In other words, plotters can read and render on paper lines and curves, whereas regular printers use raster files, which represent images as connected dots or pixels. Vectors can be scaled at any size without losing clarity, but raster images get distorted when enlarged. For this reason, PLTs are extremely convenient for printing architectural projects, as well as for posters and banners, or other types of large-scale graphics.

There is also a downside, however. The use of HPGL (Hewlett-Packard Graphics Language) often implies sending arbitrary sets of output lines to the plotter, which means the machine wastes a lot of time skipping between lines and ends up being less effective. With reaConverter, this problem can be fixed in no time! By using the PLT optimization feature, you can make sure lines and curves are sent to the plotter in a sequence that requires a minimal amount of skips. Thus the process becomes better timed and effective.

Install reaConverter

Here is how you can convert a PDF into an optimized PLT in a matter of seconds.

Load PDF files

Start reaConverter and load the PDF you intend to convert. reaConverter can also handle batch conversion, so feel free to add as many files as you need. You can select them manually or drop them directly into the reaConverter window. When you have to deal with large quantities of PDFs mixed between other formats in a folder, the Advanced file select can come in handy, as it lets you automatically select a specific extension.

Create optimized PLT files

In the Saving settings tab, choose the format and location of the output images. Pick PLT from the buttons placed in the lower part of the window. In case it isn’t there, click the Plus button and you will get a full view of all output formats supported by reaConverter. After you pick PLT, move the pointer on the button and click on the Settings icon, placed on its upper left side. Click it and then tick the box next to Create optimized PLT. You can also reach this window by following this path: Menu → Saving settings → Format saving settings → PLT

Then pick the location of your output file — in a local folder of your choice or directly online, using one of the supported storage cloud service.

Finally, press Start and your plotter-ready files will soon be done!

Video Tutorial

Advanced users can handle PDF to PLT conversion using command line interface or DLL in manual, automated or scheduled mode. You are welcome to contact our technical support when you have any questions about reaConverter.