(Migrating from S7-300 PLCs to the current S7-1500 range, I found the complete documentation package for the 1500 universe in one whopper of a pdf. Just north of 11,000 pages IIRC.)
I shared the OPs frustration when working on the S7-300, though. The docs are excellent, there's just so many of them...
I don't know if it ever got fixed. I stopped using Linux around the time when it was introduced, and having had to revert to using xpdf for browsing large PDFs like it was 1994 again was part of why I ragequit :-(.
It took some time for it to land though and not without the kind of discussions that you see on the Gnome bug tracker. It was pretty disheartening.
I like it so much in fact that I've been looking for a linux alternative and haven't been satisfied yet. I will try evince though.
Now? Eh, Firefox. If that doesn't work, well, find an old Mac which hasn't been "upgraded" I guess.