Watermark is basically protecting your photos from being stolen and used by others and assumed as owners of your photos.
One way to protect your photos is through image software such as Photoshop or CorelPhotopaint.
1. How To Add a Text Watermark Over a Photo in Photoshop
2. Watermarking your photos in Photoshop 7 and CS
3. Add A Copyright Watermark Pattern
4. How to Add a Watermark to Your Photos Using Photoshop
5. How to make a simple watermark in GIMP
6. GIMP Tutorial – Watermark Photos
7. How to make your own Watermark using GIMP 2.6
8. How To Add a Watermark to a Photo in Corel Photo-Paint