I have used the Simple Scanner (really nice app, by the way) to scan some sheet music. Looks nice but it's picking up too much detail and would like to adjust the levels.
Sadly, the GIMP fails so miserably here that it's unacceptable to use it. The PDF programs in the software-center are all incapable of doing that as well. I've looked at PDF Studio (the commercial linux PDF editor) and it doesn't look like you can do that as well.
Am I doomed to use a friend's photoshop in Windows?
This will be for a high quality, 50 page document. In GIMP, one must edit each individual layer. There is no batch processing applicable (unless I'm missing something). Further, I cannot export as PDF (or .ps or DeJaVu) again. Please, no roundabout workarounds (I intend on editing about 100 50-page documents and would rather not spend time fiddling around with programs that aren't suitable).