How to Restrict User from Convert Quote to Invoice or Print PDF?

Just wonder if we could set security group or role to restrict certain user from printing PDF from AOS modules?
I think that it is important to be able to restrict certain user form converting quotation to invoice too. Normally, we expect invoice to be generated only if the quotation is approved by superior and confirmed by customer.
Any advise please?

Check out this thread on the old sugar forums for some advice on how to do a role check on a specific button. The last post should be of most help

http://forums.sugarcrm.com/f3/hide-display-custom-buttons-conditionally-contacts-detailview-85635/