Re: Name one
It is not about programs that can _view_ PDF files. It is about programs that can: [1] Allow you to complete PDF forms. [2] Allow you to annotate non-form PDFs, so you can fill in forms that were meant to be printed.
That's fine. By all means, point me to a platform that doesn't have applications that can handle PDF forms and annotate PDFs, but does get modern versions of Firefox.
Personally, I've always hated the Firefox PDF viewer, as it quite often doesn't print out PDFs as they are formatted, which is the #1 feature PDFs have going for them. Disabled it across my company, to eliminate all the regular complaints that PDFs (that my program generated) were cut-off when printed, as well as terrible performance on very large PDFs. I'm happy to try it again to see if they've improved things, though I don't see any compelling reason to when the native PDF viewer works great (on all platforms).
The *only* Linux one I could find that could do both was Okular, which is ugly and needs hundreds of megs of KDE libraries installed.
Fortunately you found one.
I'm not sure why you need ONE app to be able to do both, when we're talking about lightweight free apps. That sounds like the Windows mindset. In the Linux world, I'd go straight to a fully capable PDF editor, instead of using a tacked-on annotation feature in a crippled "viewer" app.
Personally, I open PDFs in Xournal if I need to edit, erase, draw on, or annotate them. Well known and even more capable PDF editors include Inkscape, Scribus, LibreOffice Draw, and Qoppa.