A friend of mine has been doing some volunteer work lately, photographing gravestones and gravesites. Since these images end up on a website, she asked me about watermarking her images - something I never do (no surprise since I rarely post photos to the Internet - although that may change soon). I've seen some images from forum members that include watermarks. Does anyone have an recommendations on how to go about it or which service to use? I doubt she wants to purchase Photoshop or Lightroom - although she has iPhoto on her Mac.