I'd like to make colour adjustments to an existing PDF file, the equivalent of Photoshop's adjustments, and save a new version with the altered colours. I'm after more than a colourspace conversion. I'd like to take a file that's black and white, and convert it into green, blue, yellow, pink etc versions. It's upwards of 100 pages full of text and graphic elements, so doing it by hand isn't really an option. Is there any way of achieving this?