Signatures - when I "mark as read only" file is too large

I am using Adobe 9 Pro to create a form and it works fine. When I change the "signed" properties to "mark as read only" the fields that the user completes, it makes the file grow to a whopping 2+MB file.

Any ideas on how to trim this down? My next step will be to allow Adobe reader to be able to save the form but it's too large to be usable at its current state.