Sonny Software

Hi,

It might interest some of you that this open-source PDF viewer allows you to annotate your PDF articles, much reducing the need to print them. It becomes particularly useful when used in combination with Bookends, which manages your collection of PDF articles.

http://sourceforge.net/projects/skim-app/

Denis Chabot

This does look like a very promising app. One thing to note, which may be an advantage or a disadvantage, depending on your needs, is that the annotations will not be visible in other pdf viewers such as Preview, Acrobat Reader etc.