PDF Reader That Is The Best For User Privacy?

Good morning,

I did an intense search but I couldn’t find anything related to PDF Readers.

I thought this question deserved its own thread because more and more books and documents are ONLY being made in an electronic format such as .PDF. Physical books are definitely on the way out and even when they’re an option to buy alongside the ebook version the physical books are MUCH more expensive even though the ebook version and the physical book contain the exact same text…

My number one concern is that the PDF file that I’m reading is known to me and me alone and that my PDF reading activity isn’t uploaded to anyone online. Adobe PDF Reader seems like the worst possible choice in this regard.

My LENGTHY research has led me to confirm that this is the best PDF Reader for user privacy and user security: Free PDF Reader - Sumatra PDF

What do the privacy experts here think?


My second concern that is extremely worrying to me is that it’s possible for Amazon to alter text within ebooks AFTER a user has purchased it via their Kindle platform.

For example: an ebook is altered 5-10 years after being purchased because the ebook’s contents have now been deemed to contain controversial text and so it is removed and unable to be viewed by the user who purchased it.

Real world example I found: Reddit - Dive into anything

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In the website you linked, I could not find any hint of a privacy policy, nor one in their GitHub Readme. If I have to go anywhere further than that, then that is a big problem.

You didn’t mention the operating system on which you want to use a PDF reader. The concern you express here is not an issue on Linux distributions (which can cut off network permissions to Flatpak apps via Flatseal or KDE System Settings) and GrapheneOS (which can cut off network permission on app install).

Since you didn’t mention the OS on which you want to use a PDF reader, I second the recommendation @KDEBacon offered, which has a robust privacy policy that is featured and linked in the main app page (under the ‘Free Software’ heading). There is also the GrapheneOS PDF Viewer for Android.


I appreciate your reply!

Sumatra is open source, but it’s only available on Windows because the developers are only familiar with Windows.

The source code is completely available so I think it’s safe: GitHub - sumatrapdfreader/sumatrapdf: SumatraPDF reader

It’s also available in a portable version that can be run from a USB stick: Sumatra PDF reader download page

Here’s a review that I think gives an accurate description: Conclusion: If you just want to read PDF files, use common basic features, appreciate a minimalistic design and low resources usage, I recommend and rate it as being the best ultra-lightweight PDF viewer.

Link: Sumatra PDF download latest version

I just made text italic that was written by the reviewer.
I just added a quote from Redoomed.

Typically, I’ll either use the built-in reader (like Preview for Mac) or my browser (LibreWolf, on Windows).

My use-case is a little more demanding… I need a PDF editor that can replace Adobe Acrobat to create PDFs from Word documents (or similar) with fillable fields. It’s slim pickings out here…

Stirling PDF is the only FOSS editor that I’ve found so far, and it’s more of a toolbox, so I’m not sure it’d work for you. I’ve heard CutePDF and PDFelements from Wondershare suggested, but those aren’t OSS afaik.


Lots of options are listed here, i dont know if they work with Windows though: PDF, PS and DjVu - ArchWiki

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[quote=“Redoomed, post:4, topic:15410, full:true”]

I just installed Graphene PDF Viewer on my Android phone. I’m currently trying it now.

What makes it so special in terms of maintaing user privacy and not leaking what PDF files are being read by the user?

The app doesn’t require any permissions. The PDF stream is fed into the sandboxed WebView without giving it access to content or files.

Quoted from GitHub - GrapheneOS/PdfViewer: Simple Android PDF viewer based on pdf.js and content providers. The app doesn't require any permissions. The PDF stream is fed into the sandboxed WebView without giving it access to content or files. CSP is used to enforce that the JavaScript and styling properties within the WebView are entirely static.


I’m not into these books, but I just came across this article where ebooks were deleted from people’s devices…

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Sumatra FTW.


I’m starting to think the best thing to have is an excellent Windows Software Firewall and just blocking 100% of all communication from the PDF Reader App to the Internet to prevent the PDF Reader App from transmitting personal user data back to the Internet?

I hope I’m not breaking any rules by posting this but it seems like the best Windows Software Firewall I’ve come across: GlassWire Premium Features

It’s only $3 a month per Windows device as well

I just re-read the site and it’s also available for Android which is great because I know many users here use Android

From all my research, this would seem to be the best ideal setup to prevent PDF Reader Apps from contacting the Internet and transmitting personal user data:

  1. Choose an app that values user privacy and says that they will not transmit . It also needs to be confirmed by people like the security experts on PrivacyGuides that it is in fact safe and does not transmit data.

  2. A reliable firewall that blocks all communication between the PDF Reader App and the Internet

I guess I’m trying to say that this would give a “dual layer of protection”?


in-built in Browsers are pretty good these days.

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For Android : GrapheneOS PDF Viewer

For PC : your browser


I appreciate your replies!

I;ve installed grapheneOS PDF Viewer on my Android device and I’m testing it out now.

The problem with me using a web browser is that Firefox recently made it possible to edit PDF files inside the web browser: Add text to PDFs with Firefox PDF Editor

Sumatra still seems like the best choice for Windows PCs since it’s open source and has a big community? However, is it a good idea to allow Sumatra to update itself?

Regarding browser PDF Readers:

It just seems like a bad idea to use an App like a web browser to read PDF files because web browsers are designed to send data traffic from the user in the form of outbound data and inbound data from the Internet?

It seems so easy for a web browser to send personal information about a user to someone on the Internet? In other words, behave like a trojan in it’s default behaviour?

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When I bought Michael Bazzell’s pdfs I needed to fine something better than the stock app. Book Reader is what I settled on. Also opens many other formats.

It’s a simple app with fewer options if you consider that a feature.

Edit: I see you didn’t specify a platform but I’ll leave this here anyway.

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can test it with wireshark, it should not connect to any suspicious domains but can never be sure.

If you are trusting the software, you should trust the domain :man_shrugging:

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Actually I think that using browsers to open pdf files is not a bad idea security wise. They are sandboxed, constantly updated and you don’t have to trust another app, minimizing the attack surface.
Unless you need some advanced features I see no good reason to use a dedicated software.