Creating a signature or watermark in Elements 18?

I would like to add a watermark or signature to some of my photos. I read that I can go to the "type" box in editor and simply write or type what I want. I have done this but note when I do, it saves the one copy with the signature and is how I would like it but leaves a copy of the original one as well. I really only want one with my signature or watermark on it. Can this be done with some of the watermark programs that are on the market or is there a better way to do it?