[pdftex] Switching paper tray (was Duplex printing?

[Peter Flynn]

I have had a request for an application to generate PDF files for
printing on a machine with preprinted stationery in the top tray
and plain continuation paper in the bottom tray.

As switches like this are usually done via a driver, is there a
standardised way in which pdf[la]tex can communicate paper-tray
switching to a printer yet, or does it have to be done with
\pdfspecials?

///Peter