I used to use a program called iAnnotate. I now have the free Xodo in my Lenovo laptop as an app. I used to be able to make stamps (i.e., a comma with a circle around it because I use that annotation all the time in my proofreading).
I have looked in the help sections, but I don't see specifically whether the rubber stamps are only for the paid/Pro version.
I can't figure out how to use them if I am able to under the free version.
The rubber stamp feature is available on the Android APP, and it will be coming to the Windows APP soon.