- Hewlett-Packard Color LaserJet User Guide

90 Common printing tasks EN
To use the optional duplex printing accessory:
Be sure that the optional duplex printing accessory is installed
correctly. If the 500-sheet paper feeder (Tray 3) is installed, the
duplex unit must be positioned between the printer and Tray 3.
Verify that the printer driver is configured to recognize the duplex
printing accessory. (For instructions, see the online Help for the
printer driver.)
Close the door to the rear output bin. The rear output bin is
located at the back of the printer.
Select the appropriate duplex options in the printer driver
software. Duplex options include the page and binding
orientation.
Duplex printing is not supported for certain media types, including
transparencies, labels, and cardstock.