How do I Flatten of lock a PDF File once it has been submitted via Email.

[Cparkridge]

I am trying to create an online form that once you click the submit field the information entered to the form on the PDF is locked or not editable once it is emailed to the person to receive it. 

[try67]

The best way to do that is to ask the user to digitally sign the file before submitting it. Anything else is easily overcome by someone willing enough.