Lock fields after send a PDF file

Hello all,

I have done an application that consists in fill in many fields using Adobe LiveCycle Designer 8.0 program.

After many fields are filled, I click on a Regular button that sends an e-mail.
When I receive the e-mail, I download the attached pdf file to a determined folder.
The problem is that when I open this generated PDF I am able to edit the fields.

Is there any way to lock fields after clicking the Send button?

Thanks in advance.

Best regards,
Roberto