Sometimes I get PDF files generated from PPT that have a dark background with a pattern. These look hideous in print.

Acrobat Pro allows you to edit such documents to make them look better in print.

To remove background, Tools->Content->Edit Object. Rubber band select narrow strips around the edges to select most of the background objects while avoiding main content. This removed 90% of the background for me. Some pages needed a touchup.

Voila! Now you have an actually legible PDF.