Photo Editing – Watermarked images before printing

I have a job and would like to add a number in a sequence as a watermark on the photos before they are printed. What I mean by that is, when I upload them, I want to add a sequence of numbers to the actual photo and be there when I print them. Which program can do that? I tried to search for answers but did not really find anything with what I'm looking for.

all help and suggestions are appreciated.