It looks like the default window height when opening many PDF files is ridiculously too small. I don't know whether some PDF suggest a default size or not, but in many cases it is far from optimal.

Open this document for example (I can provide and even create others if needed):
http://people.gnome.org/~michael/data/2012-02-04-easy-hacks.pdf
(You need a doc you never opened because Evince remembers the window size of the last time you viewed a doc.)

If we're not able to guess a reasonable size, then I suggest Evince opens maximized instead; the current situation just makes GNOME look plain silly in too many cases. ;-)