How to add copyright info to drawings?

[thedqs]

I think all you would need to do is in Windows Explorer right click the file and under properties enter the copyright information.

[jtwitchell]

You may want to look at the Creative Commons License. They may have suggestions on how to apply the license.

[JPratt-p40]

Perhaps this isn't what you need, but if you want to add a small line of text to an image, such as a copyright notice, here are two free image editors with that ability:
gimp.org/windows and getpaint.net (for Windows)
If you need to convert the image as jpg or png, here is a free tool that installs as a "printer" that can make an image or pdf file from nearly anything that you can print: pdfforge.org but I assume xnview.com is superior as an image conversion tool.