HP LaserJet 8000 Multifunction Printer series - Manual (Page 105)

Chapter 2 Printing Tasks 105
Printing Both Sides of Paper (Optional Duplex Printing Accessory)
z
Load letter and A4 paper with the side-to-be-printed facing down, and the
top, short edge toward the back.
z
Load other sizes with the side-to-be-printed facing down, and the top, short
edge toward the right of the tray.
All other trays