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
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.
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.
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.
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.
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
Edit: 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:
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.
A reliable firewall that blocks all communication between the PDF Reader App and the Internet
Edit:
I guess I’m trying to say that this would give a “dual layer of protection”?
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?
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?
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.
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.
