Printing current date and time on each page

Question

I'm often printing several versions of a document (e.g. a paper in progress). To keep track of the printouts I would like to print the date and time of printing onto each page, regardless of which application I'm using (although it would be okay if it works for PDF files only, if it happens automatically). I have seen Windows printer drivers including this feature, but haven't found any settings here (e.g., Canon iR3225) nor any hidden-CUPS-feature-I-could-activate-in-the-config-file.

Any ideas? Some sort of preprocessing I could inject into cups?

(I'm using Mac OS X 10.6.7)