Rather than writing a driver, consider using the PDF Services feature of OS X print dialogs. In either the system-wide /Library/PDF Services or a user's ~/Library/PDF Services directory, you can put AppleScripts, Automator workflows, or symlinks/aliases to applications or folders. Those items will appear in the PDF pop-up menu in the print dialog, and if the user selects the item, a PDF of the file will be placed in the folder or be passed to the application, script, or workflow.
