I was reading a pdf of a book that was a little spicy. And I noticed the amount of added extra's that adobe has now with it's ai summaries and inbuilt web searches, even the page number field is difficult to use with bloatware.
It struck me that if I were to read something of a "banned book" list, like catcher in the rye, I wouldn't particularly want adobe to monitor and send back what I was reading. What would be the best way to read PDF files that's localised entirely to my machine? a pdf reader and nothing more?
Okular is the KDE one. It's common in a lot of Linux distros, and open source so you can be fairly sure it's not phoning home.
I don't know if I'd call it the best. But it's an option.
If that's not to your taste, check pdfreaders.org for a big list of them.