Testing

Save your money!! (or how to get digital watermarking without having to buy Digimarc)

There's no reason you need to wait until you get something like Digimarc when there's already free software out there that can do that just as well.  You'll want to look up something called steganography.

I have a few suggestions:

• steghide: I use this one personally.  It's pretty easy, although it doesn't exactly have a pretty graphical interface.
• Digital Invisible Ink Toolkit: I've not used this one, so I can't tell you from personal experience if it's any good, though the documentation is pretty good, which usually indicates a good amount of quality.
• StegoMagic: I'm not so certain of this one.  There's not much information on it, so I can't judge its quality, but it is the only one of these three that seems to have a nice graphical interface.