Adjust colour, brightness, sharpness, etc.
Adding notes with leaders to objects in the images.
Highlighting specific areas of interest.
Making pictures of your boss look much meaner and fatter.
Swapping peoples bodies and heads?
Seems to me that most of what you need is Acrobat or a reasonable facsimile. If these are indeed reports, then they need to be readable as reports. If they're being scanned in, then most of the contrast, etc., need to be fixed at that time. In fact, you can usually scan directly to PDF, if you have the appropriate software.
For those wanting to try a program that can "do it all", this is essentially an open source equivalent to Adobe PhotoShop. I am in my infancy of doing much with it as there is so much in there.