I keep thinking about putting together either a blog or just a series of "PDF info" posts. I'm mostly not sure what to include.

The main useful PDF function I haven't seen in free (or cheap) software is bookmark editing. There's some that'll remove bookmarks (which is brainless; printing to a new PDF will do that), and there's cheap programs that will split a big PDF by bookmarks; extracting a list of bookmarks and editing current ones both seem to require either Acro Pro or one of the *expensive* alternates. (Foxit Pro, maybe? I haven't worked with that one.)