I don't really enjoy Evince, and I use Okular for my pdf needs.
Okular is nice, but when I open a document with it, it's not added to my recent documents, nor appear in the fast dash file search (it does appear after a while when the locate search is activated).
I expect Okular to register his things with Nepomuk instead of Zeitgeist.
Is it possible to get either Okular or Nepomuk give that info to Zeitgeist?
Sadly at the moment it is not. The integration of Zeitgeist with KDE isn't that good. It needs more work.
More info
There is a library named
libqzeitgeist
which can be used for gluing applications with zeitgeist. Sadly the library (gluing code) exists, but not used that much. I had plans on working on it, but got stuck up in other work.