When I want to review and annotate, or mark up, a PDF, I do it almost exclusively on my iPad.
For me, it is a nice all-digital workflow that avoids the print-out-and-write dance. I can then save or share the annotated PDF right from my iPad.
There are many apps that can do this, such as iAnnotate, PDFpen for iPad, and PDF Expert, but the one that I am used to is called GoodReader. GoodReader is the one that is shown in this video, but the general concept is similar.
I assume that this can be done on an Android tablet as well. If you have an app you like for this, please leave a comment and let us know.
(Photo by TheMacUniverse)
This video on annotating a PDF on the iPad is part of a series of quick videos on paperless tips and topics. View more in the series here.