There's this pdf/epub/djvu (.etc) reader called STDU viewer which I'm really liking right now. Its winning feature for me is that you can export the portions of the pdf/epub/djvu which you have highlighted into one text file. The text file has the highlighted portions complete with the page number where they appear in the document
I use the highlight tool a lot when reading pdf's etc., and this just makes collecting quotes from a novel or an academic work way easier.
A negative point however with STDU viewer is the lack of a note/comment function like in Okular. Also, it's only available in Windows OS.
Overall, it's one of the best multi-format document viewer I've ever used.
I have an Adobe Acrobat reader installer permanently stashed away. If something comes along that I have to digitally sign (government, etc.), I install it, sign the thing, uninstall again.
The rest of the time, very happy with Firefox's native PDF reader and free STDU Viewer.
If you're on KDE, you shoud give a look to Okular, it's pretty nice.
If on windows, then check this one http://www.stdutility.com/stduviewer.html It's fast, lightweight and support multiple formats