Skim is a excellent PDF reader for the Mac.
I love PDF, I read stacks of documents via PDF, I print a lot of stuff to PDF and try to print to paper to read/review documents.
However, I loathe the bloated Adobe Reader, and until now used Apple’s Preview (which is fast and lightweight).
But this new Skim reader is superb – it’s got really good annotation, a decent full screen/presentation mode.
Ace. And it’s er, completely free :-)
(Via Daring Fireball.)