I recently tried to print a PDF-document with added stamp annotations and was unlucky.
Neither in the print preview nor in a print-to-file-process (supposedly provided by my CUPS server) any of them were visible.

Some details in advance:
I used a single PNG greyscale image for several instances of the stamp which I did not rescale or distort.
I did select the "print annotations" option in the print...-dialog, as other annotations were visible.
The placement itself was no problem and the stamps then were properly displayed in the main window.
The basis of the document (without annotations) cosisted entirely of images, not text, since it was like this when I used the Google-calendar-print->print-to-file function to get the list that i was using the stamp-feature with... if that matters - or to imply my use-case