Signatures & Watermarks?

Hi folks. Do any of you know of any software that makes it easy to add signatures or watermarks to your photos, preferably free and also with the ability to use your own font style. I have a friend who's daughter has a small business which is run from her house and she has asked me if this is possible. I know I could do this with photoshop but she's the type of girl who likes to do things herself if she can. She has lots of photos to do this to and I suspect a batch process would be the quickest way to do it. Any advice or suggestions would be very much appreciated. Thanks in advance. Paul