Another option you can try is that if the document has been Reader Extended and the user saves the document, force them to save it as a Static pdf. Then they should not be able to change the form.
I am interested in your script.
Also, could you tell me if your script would work with a fillable form that uses pagination. We have a fillable form that the pages fillable are dependent on one of the radio buttons selected at the beginning of the form. Once a selection is made the form is refreshed and the pages are chosen based on that radio button selection. After the form has been filled out we would like to save the completed form as a non-fillable form. However, everything we've tried so far to save the form as non-fillable continues to break the pagination. When we open the saved form it continues to display all the pages of that form regardless of the selection made at the time the form was fillable. Perhaps this is altogether another issue. Any thoughts would be appreciated.