If you're interested in Nova Praxis, and you can tolerate the sound of my hillbilly accent, you might want to check out the attached video.
In addition to the standard linked table of contents and cross-links throughout the PDF, this video shows off what else the Nova Praxis Augmented PDF can do.
Now, whether not you can actually do all of this with the PDF depends a lot on your reader. I was using Adobe Acrobat in the video. On the iPad I use Goodreader. It can do everything except fill out the character sheet.
If anyone has any suggestions for good PDF readers to try, feel free to post them in the comments.