If you want to read, comment, annotate, fill ... meaning you can no longer use the software to create PDFs. For a free PDF reader with editing, signing, and a whole host of other useful features ...

There is a free PDF editor already available on ... move things around, and so on. The software also supports extensive annotation, including shape insertion, highlighting, underlining, striking ...

Macworld At a glance Expert's Rating Pros ・Offers a wide variety of editing and annotation tools ・Has a modern user interface ...

So what I was looking for was a single app capable of pulling documents from Google, MobileMe and Dropbox, rendering them (even the large ones) with a crazy-fast engine and letting me annotate them.