Create encrypted PDF invoices or quotes, receipts

Hi,
It is a fantastic software. recent development have been even more cool.
I have one query relating to pdf files created by software.
I would like to encrypt (password protect) so that the pdf file sent by directly email or locally created by Manager are protected against copy, or edit. I would like my clients to just print only.
So, Can we add a facility to protect pdf files created by Manager.
Thank you/