Sumatra PDF

A little bit of history

The Portable Document Format (the shortcut for PDF) is older than 99.9% of all Internet users. I've read somewhere (I can't remember the exact source that in 1990 there were around 2 million Internet users, or better said, people who had access to the Internet. That was around or less than 0.05% of the global population.

If I remember well, like most software titles, I installed the first version of Adobe Acrobat between 1997 and 1999, but I can't remember the exact order. It was either delivered from a Canon inkjet printer or from a CHIP magazine. I think 50% chances it was on the CD from a Canon BJC-2000 inkjet printer.

Anyway, I know for sure that you needed the program to read the "Electronic User's Manual" - usually it was the "modern" way back then to show you some nice pictures along with the text instructions.

Of course, it became a second nature for me to install Adobe Acrobat Reader after each new Microsoft Windows fresh installation, as most software titles had an electronic user manual and back then the Internet was expensive, slow and the number of websites was limited.

So, what I am trying to say is that I "associated" this program with a pair of lenses - I need it because the information was there and sometimes it was the only one - my first computer was a Compaq Presario Pentium 1 75 MHz with 16 MB of RAM and I think I used it offline for years.

Each time I needed access to the Internet I had to go to an Internet Cafe or to the students campus. My cousin was "connected" to a local LAN which had very slow and limited access to the Internet but it was the heaven of file sharing - movies, music - it was all there but that is another story.

So, the years passed, after 2021 the Internet literally started to explode - dial-up home (still a luxury), the same ISDN, then ADSL, cable and finally the king of all - optical fibre.

PDF - the standard was everywhere and of course there was only one main program back then (at least for me) - Adobe Acrobat Reader.

I still remember when Adobe Acrobat Reader started installing three helper services, a browser extension I never asked for and a cloud sign-in prompt that appeared every single time I opened a PDF. This was around 2013 or 2014 maybe. I was trying to read a bank statement. Nine hundred megabytes of software for that.

So I said to myself - that's it. I uninstalled it in a rage and started searching for alternatives. That is how I found Sumatra PDF.

Nearly fifteen years later it is still sitting in my startup folder.

Another little bit of history (the accidental kind).

Sumatra PDF exists because of a failed Palm product nobody remembers. Back in 2006 a developer called Krzysztof Kowalczyk was working at Palm on something called the Foleo.

From what I read about it, his job was to write a fast PDF reader for an ARM device. The processor was weak and the coding tools were bad so he moved his work on Windows to test the Poppler library. Palm cancelled the project but he kept the Windows code and Sumatra PDF was born. He named it after Sumatra coffee (just like Java or Mocha). This is a solo project maintained for two decades without any venture capital or ads.

As soon as the setup finished, I noticed the low resource usage. The installer is under 15 MB because the author used the native Win32 API in C and C++ instead of Electron frameworks. He also switched to the MuPDF engine (from Artifex Software) which is very fast. You can open a lot of file types: EPUB, MOBI, CHM, DjVu and CBZ comic archives. He removed the proprietary unrar library in version 3.0 to keep everything open source.

There is no Linux or Mac version. Cross-platform GUI layers slow down the performance so he refused to build them. If you use Linux you can try zathura. On Windows the legacy OS support is great. I tested version 3.1.2 on Windows XP and current builds on Windows 7. I still run a Windows 7 virtual machine for an old 2011 accounting app and Sumatra works perfectly inside it.

What you can do: academic users can use the bidirectional SyncTeX support. Compile a document in VS Code and it jumps to the exact highlighted line. Double-click the PDF and the editor returns to the source code. Adobe Acrobat locks the PDF file while opened and ruins this process.

Working with the program: for a long time this was just a pure reader. Version 3.3 added annotations so you can highlight text or add boxes. It does not support interactive XFA forms, digital signatures, 3D PDF viewing or OCR.

Security: The program does not have a JavaScript interpreter. Most malware exploits use JavaScript so if you open a bad PDF file here the malicious code cannot run. The portable version does not write to the Windows registry. It stores the recent files list in a text file named SumatraPDF-settings.txt inside its folder. You can also run it in Restricted Mode (using the command line) to disable printing or URLs.

I saw a couple of binary hijacking bugs in 2026. Someone could drop a fake explorer.exe file in the PDF folder and trigger code execution if you clicked 'Show in folder'. It was patched fast by forcing absolute paths to system32.

Annoying that it happened but at least Kowalczyk fixes things in a few days instead of Adobe's ridiculous three-month corporate patch cycle. There was also a sloppy bounds check in the MOBI HuffDic decompressor but that got sorted quickly too.

Just a personal note: While I am writing this - Anthropic released Claude Mythos - an AI that is capable of analyzing and outperform humans at some hacking and cybersecurity tasks. As far as I know several tech giants received access to Mythos - approximately 40 organizations - as an example I've read that Mozilla found 271 vulnerabilities with Mythos in the Firefox browser. Despite Adobe integrations with Claude into their apps I couldn't find them mentioned but I think they will get access in the second round of tech giants. Probably the first 40 were as a test-pilot and a second batch will come. What I am trying to say is that the Adobe's response might improve a lot. I had to write this - to be fair.

Anyway back to Sumatra PDF I haven't clicked a menu to rotate a page since they added the command palette. Version 3.7 even added a terminal toolkit. I just grep text across gigabytes of PDFs straight from the command line now. No registry keys either. You just open SumatraPDF-settings.txt in Notepad and paste a hex code into FixedPageUI.BackgroundColor to force a dark mode.

Finally

Sumatra PDF is not perfect. It crashes instantly on government tax forms though. Anything with XFA interactive data or cryptographic digital signatures breaks it.

I literally keep Acrobat installed purely for doing my taxes once a year and it drives me crazy. For heavy OCR work you will definitely need something else like PDF-XChange Editor.

Screen readers like NVDA will not work well because the engine draws pages as flat bitmaps instead of hooking the text layer. Version 3.6 fixed the 4K pixel doubling problem so the text is sharp at 150% scaling. I keep the portable version on my desktop because it opens files instantly and for security reasons.

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