Based on other reading in the TpT forums I had begun creating products in PowerPoint and I am lucky I did because it turns out it is easy to add a copyright to each page.
Here is what I did:
Along the tool bar select VIEW then within that tool bar you will see "Slide Master". Select this and you will have several different versions of blank slides. I used the first blank slide, my "master slide" and inserted a text box (the same way you would insert a text box on any slide). I then went to INSERT and selected "Symbol". There you can find the copyright symbol. I followed it with my name so it looked like this:
© Cate O’Donnell
It automatically appeared on every one of my slides! That saved me a lot of time since I didn't have to insert it to every slide by hand.
Maybe everyone else already knows this, but I was pretty excited and wanted to share in case someone else was looking for a time saver!