Most photo editing programs will allow you to add text to a photo. I do that and just make the print really light and put it across the picture in an inconspicuous place. Some programs also have the watermarking feature built in too. On my site, i just disable the right click feature and also disable the IE toolbar which allows others to copy or print. The watermark isn't 100% foolproof, as nothing is but it is better than nothing at all. Good luck!
