Most of the watermark software you run across isn't free so Google searching it is a crapshoot. I've been debating on using watermarks for the photos I've been taking of my son's hockey games because one parent like to spread them all over her Facebook page and not give me credit for them. I just paid $3 for a program called "Bulk Photo Editor" by SkyOnTheWay from the Google App store and I'm using it on my Win10 desktop. So far, the program has been great at letting me take multiple images and adding text to them all at once.