I have some photos in f-spot that I want to print, 4 to a page. But when
I try to print them, the printer does nothing. I suspect that the photos
are too large for the printer to handle, so I want to tell f-spot to
reduce the resolution on printing. Is there a way to do that?

I don't want to change the resolution of the photos themselves, just
what gets printed.

I also tried printing to a PDF, which worked. But when I try to print
that PDF, it fails in the same way. So is there a way to postprocess
images in a PDF?

Cheers, Dave