Today I learned to put embed copyright info in the picture in Lightroom, not watermark. I have watermark on the photo. But copyright info is embedded in meta-data (Exif data), so even if people crop the watermark at the corner of the photo, the copyright info stays with the photo.
There are many links when I googled it and they all have the same procedure. During import, apply a a user-defined preset with IPTC copyright section filled.
Some here: http://laurashoe.com/2012/01/02/have-you-created-your-2012-metadata-copyright-preset/
What about those photos that I imported earlier without copyright reset? The metadata doesn't include copyright. So to apply copyright on them, use "Sync metadata" with the ones that has it.
Instruction here: http://www.adobepress.com/articles/article.asp?p=1151024&seqNum=3