spending a lot of time looking at pdfs in evince/okular/acroread can get old pretty quickly... zathura is

...a highly customizable and functional document viewer. It provides a minimalistic and space saving interface as well as an easy usage that mainly focuses on keyboard interaction.

which, it pretty much is.. using a zathurarc you can define a colorscheme to make reading pdf's etc a bit easier on the eye, for example, setting

set recolor_darkcolor #999
set recolor_lightcolor #333
set recolor

in $XDG_CONFIG_DIR/zathura/zathurarc makes your {pdf,djvu,ps}s look like:

which is nice, and having vim bindings in more places can never be a bad thing