PO's and Purchase table header permissions

I am trying to create a role that can print Purchase orders but not to be able to modify any information on the PO.  Why does this role need modify permissions to the Purchase header table?  Using NAV 2009 SP1, the problem is that i do not want the user to modify the Purchase header in any way just to print out the PO's.  I keep receiving the error on print "You dont have permission to modify the records in the Purchase Header table"