Ok, I think there is a little confusion, I beleive reimerron is refering to the "mounting board" not the window mat itself. Am I wrong?
Reimarron the only prints I have seen where the signature is right on the same paper as the print are those from Dan Burkholder. With pt/pd this is easy as you "mask" when the image is being printed and it leaves a white border around, where you can sign. For silver prints I have never seen anybody sign on the print itself. Does not sound like a good idea to me any way. what kind of ink will you be using? Is this ink archival? I dont know seem like it is not good advice.