How can I sign my photos for copyright?

There are a number of watermarking apps that can do that. Go go MacUpdate.com and search for "watermark".

There's a free iPhoto extension, Border FX Exporter, that can add text to your photos when you export them out of iPhoto.

Preview's annotation feature can be used to add text to a photo. Preview can be used from inside iPhoto as the external editor to do that annotations and it's included with the system.

Lastly, 3rd party editors can add text to photos.

Some Image Editors That Support layers:

Photoshop Elements 11 for Mac - $79

GraphicConverter - $40Rainbow Painter - $30
Imagerie - $38
Acorn - $50

Pixelmator - $60

Seashore - Free

GIMP for Mac - Free

Xee 2.1 - free

Thank you. I will look into the apps that you've mentioned .

🙂