I'd like to be able to password protect or encrypt my PDF file so that no one can possibly modify my fields or calculations, scripts and fields using Designer. That is, after I add fields to a PDF form using Designer, I would like no one to be able to load this form in their designer and modify or copy an of the work I've done.
Although, I'd like for anyone to be able to still fill out the form using adobe reader without having to enter a password.
I do this all the times... I protect my work by adding design level password at File>>Form Properties>>PDF Security. Password is requested at the time you save your design after you check the checkbox in this tab. Just try it first on a test basis before you actually use it. I have designer 7.1