I wrote another post for LifeHack.org:
Back in the day, we all reviewed and edited documents with a red pen, highlighter, and sticky notes. Then came track changes and comments in MS Word or maybe you used the Review tools in Adobe Acrobat to annotate comments and edits on a PDF while sitting at your PC or Mac. Now we can use an iPad and iAnnotate PDF, a powerful alternative to GoodReader. The document reviewing process has gone from paper to PC and now to iPad without missing a beat.