Can't use Optimizer to check why form is almost 10 times bigger than it should be

I have created a form with Reader Extended Rights to allow the users to save the completed document. I have reports from users that the form, which starts out at 235MB, when saved/emailed is over 1.9 MB. These forms have check boxes and text fields but would not usually have more than 200-300 characters typed into the various fields. Because the forms have Reader Extended Rights, I am unable to use the Adobe Optimizer as others have suggested; trying to do so gives me an error message. Any thoughts, suggestions for how I can find the underlying cause of this?