You can't read a PDF outside of a PDF reader.
Yes you can.
The preview pane in every file manager I use will display the PDF (Mac Finder, Windows Explorer, and Google Drive).
Preview, which comes installed on every Mac computer is an excellent PDF viewer with a lot of editing and markup features.
Most Web browsers will display PDFs and are increasingly the default PDF readers for many people. Actually, I find it annoying how when I download PDFs they keep opening in my browser instead of Acrobat. Seems like I have to keep revisiting my OS and browser settings to fight that.
There are MANY PDF viewers and editors available, including open source options.
Many e-reader devices and software support PDF.
You have more options for reading and interacting with PDFs than almost any other file format other than TXT.
Yes, there are lots of apps that have PDF reading capability.
Exactly.
Tell me how I'm going to easily access my Warhammer Fantasy content in Foundry outside of Foundry without a lot of time and effort to convert it. Ignoring prepped maps completely, as that is not content from the physical books, I can export journal articles to HTML. I can export character sheets, NPCs, items, spells, etc. to JSON. How do I piece that all together into readable book-like format? Migrating that into another VTT platform will take coding work. And I'm sure that as the Foundry modding community comes up with clever solutions, IP owners are going to require Foundry to add measure to counter that.
The only way the ensure my foundry content remains available long into the future, for a reasonable amount of effort, would be to keep installation files from different versions and backups of my content. And if the company ever goes out of business, or bought, and support ends for the product, then to make a VM of the then-current operating system and installed software, with my content, to ensure I can continue to run the software over the years. How many consumer want to even deal with that?
And this isn't a far-fetched scenario. Already, you have to be careful to back everything up when Foundry has a major upgrade. Even if you don't use any mods (which make things more complicated), upgrades can still break purchased content.
Any one of the current "big" VTT companies could easily go out of business and see support of their product end.
Adobe could go out of business but you'll still have plenty of free and commercial options to access your PDFs.