I'm not familiar with Picassa, so I don't know if they have that feature. I usually use photoshop because you create your watermark once, and then it is saved and you just have to click on one thing to add it to your picture. The only problem I have is that I have to move it around to put it in the best place on the picture, and sometimes I have to make the print bigger or smaller to match the size of the photo. Sometimes I have to change the color of the watermark so it will contrast with the photo. Then you have to use photoshop layer blending options to lighten it if you don't want it to overpower your pictures. I use my ebay id as my watermark.
This is the tutorial I used to learn how to do it in Photoshop:
http://www.all-things-photography.com/add-a-watermark.html
This is part of the message ebay sent me when my picture was stolen:
"While there is no foolproof method to keep other members from
downloading your pictures, you can use a watermark to discourage them.
You can add a watermark when you upload your picture to the listing
form. Here's how:
1. In the selling form, scroll to the "Bring your pictures to life"
section.
2. Click the "Add or remove options" link, and then select one or both
picture watermark options:
-- Enable watermarking with my eBay user ID
-- Enable watermarking with the eBay camera icon
3. Click the "Save" button.
4. Continue filling out the form.
You can also create a watermark with most graphic editing software. I
recommend putting the watermark in the middle of the picture. This will
make it difficult to remove the watermark without distorting the image."
I never tried ebay's suggestions, but that might be the easiest, but since I imbed all my photos except for the free one in the listing, I don't think the ebay watermarking would work for me.
I upload my photos to Photobucket. They have a section called tools, and when you select a photo, you can use the decorate function to add text with a transparent background, so you can use that as a watermark. I haven't been able to figure out how to add it to a bunch of photos at once, so it looks like you have to create it for each picture. You should see what features Picasa offers, but if you have to create it anew for each picture, then it is probably easier to do in Photoshop, if you have it, or some other photo editing program. You can probably even do it in paint.
So there are lots of ways to do it, and I am sure one of these will work for you. Feel free to ask for help from me if you need it.
