Like mwb1100, I also recommend Adobe Reader SpeedUp.  I had problems with Foxit and several other readers, converters, etc.  My use is very much like Darwin's, primarily academic journals and, very rarely, form-filling (rebate forms--gack!).  But re-tuned by AR-SpeedUp, Acrobat is fast, fully competent, and I never have to check Task Manager or Process Explorer to find what's the hold-up.  I haven't encountered the mystery zoom problem--yet.