"Native" PDF workflow through CUPS (save todisk) on OS X

[Ben BW]

> If you edited the PPD file "in place", then cupsd won't pick up the changes until you restart the system or cupsd (it doesn't know the file has changed).  Use "lpadmin" to update the PPD instead next time...

Thought I killed and restarted cupsd, but point taken.

> Anyways, you have the basics right.  The "application/vnd.cups-pdf" format has things like number-up applied to the output.  If you list "application/pdf" instead you'll get the original spool file, which is equivalent to what you get if you choose "save as pdf" in the print dialog.

Nice. So how does "vnd.cups-pdf" differ from "pdf"?
Can you point me to any documentation about all this? I haven't found much in the CUPS docs specifically about this issue, but I may have not been looking in the right place.
How might I apply n-up to the pdf format...?