What janitor said! Every single computer (and even smaller devices like iPads, iPhones and similar) has the ability to take a "screenshot" or "print screen", which basically just photographs whatever's on the screen and saves the image to the user's harddrive. So anyone who can look at your pictures on their screen is able to save a copy to their harddrive without needing to click on anything at all.
Always watermark your pictures thoroughly. If anything's online for more than 3 milliseconds, someone will have saved a copy to their harddrive. Think how many fake private gallery scams there are on AW - they must go around nicking thousands of genuine escorts' photos every week to fill up their galleries. Plus there are forums and whatnot out there dedicated to methods of stealing adult content and getting around any method that performers and providers try to use to protect their livelihoods, so no matter what fancy content protection methods get devised, there'll be an instant workaround developed, too.
However, the simplest method still works. If there's a faint but legible YOURNAME.COM written over each boob in your photos, anyone who nicks and passes around your pictures will be doing nothing but giving you free advertising.
And nobody can claim those pictures for themselves. But watch out - writing
yourname.com in tiny letters in the corner won't work, cos that can just be trimmed off and the main part of the photo stolen easily.
If you need an online editor, I would usually recommend http:// pixlr.com/editor (remove the space to get the link). They have simple methods for adding text of any kind and reducing that text's opacity (i.e. increasing its transparency), which is the best way to add a subtle, custom watermark in the best place for each individual picture. Or you can Google for apps that are specifically dedicated to watermarking photos - something like this would be best if you have a folder full of dozens or hundreds of images that need watermarking.
I would note my personal experience here: I watermark every single image I upload and I have never, EVER had a client complain. Any sane man understands full well why sex workers have to watermark their content. And if anyone did complain, I would respond (unless they were just a general "send me face pic plz" pillock) that they are more than welcome to visit me to see the most high-res version of my boobs possible.