[coolaun]

Many thanks for the detailed explanation, Mike. Nearly all my annotations are freeform, so I didn't notice the drawbacks you mention with text and stamps. 

I agree with you that this would be the best solution:

My preference is still to solve this problem without the need for embedding (i.e. to add an option to sync annotations automatically between a snippet and the original, or a way to quickly copy annotations).

Once again, thanks. I really appreciate the time you take to reply to everybody here.