I have an external 100 pages PDF document (not created by pdflatex) that I `\includegraphics` page-wise into a beamer presentation. The external PDF document employs white as page color, but I need the background to be transparent.

Ideally, this would be an option one could pass to `\includegraphics` – which I doubt to exist. However, I would also be open for some process involving external tools (`pdftk`, `pdfjam`, ImageMagick, Acrobat...).