Thanks for the reply, Ryan!
Is there any way to accomplish this without adding it to the doc? This seems like a fairly expensive way to do this.
To give some context, I am trying to keep an old copy of an annotation around for when the user modifies the annotation. For example, say a user draws a line that is colored red. They then change it to be green. I want to give the user the option to undo that modification and set it back to red. My idea was that if I had a previous copy, I could just simply replace the new annotation with the old one, effectively undoing whatever it is that they did.