Although putting your signature on the mat board is fine, I would consider signing the back as well. Although an artist mounting and matting their own work may consider the mat board part of the art, others may not. In fact the #1 goal of conservative quality museum framing is to allow the “artwork” to be separated from the backing, mating and framing so that everything except the print can be replaced at will. Many prints sold already matted but not framed are taken to custom frame shops where the mat is often discarded. It the client chooses not to discard the mat due to the signature it limits the creative choices for the customer framing trying to integrate the artwork into the clients room where it will be displayed.
Originally Posted by StigHagen