Well, here's something I wish I knew about earlier. DRAFTABLE COMPARE is a free online (and downloadable app) which compares two versions of a pdf.
Imagine...you've been prepping or working from a pdf manuscript you believed to be the final version, only to suddenly be sent a new copy that the publisher says is the actual FINAL version.
Well, with Draftable Compare you can compare the two versions and see where the alterations are. Hopefully they will only be punctuation and layout, but I think we all know it will also be editorial, right?
The online version is FREE, but if you prefer a more secure offline edition, there are apps available, which offer a 14 day free trial before asking a small fee.
Might be something worth checking out?