printers.conf getting overwritten

[Richard Cooke]

Setup a PDF printer on a RedHat server. Downloaded a PDF backend and installed it in /usr/lib/cups/backend. Setup the printer using "PostScript Printer" and as a "Networked CUPS (IPP), did not have a selection for a "Virtual Printer". Editted printers.conf to change URI line from "DeviceURI ipp://pdf:/home/$USER/PDF"  to "DeviceURI pdf:/home/$USER/PDF". restarted cups with command "/etc/init.d/cups restart". PDF printer works great from varity of applications. Problem is that if a new printer is added or modified and changes are saved, the PDF printer in printers.conf returns to "DeviceURI ipp://pfg:/home/$USER/PDF". I have then go in and re-modify printers.conf to the correct setting and re-start cups. Would not mind doing this locally since I manage local printers. But, we have remote sites where they might add their own printers and I would have to correct these remote sites.

Is there any way to 1) be able to add "Virtual Printer" to the selections, or 2) have CUPS not modify the printers.conf of existing printers, or 3)
have the PDF printer stored in a separate printers.conf and load that file  after the real printers.conf is loaded upon restart of cups?