HP LaserJet 4000 Printer Series - HP LaserJet 4000, 4000 T, 4000 N, and 4000 TN Printers - User's Guide

EN
Chapter 2: Printing Tasks 33
Paper Orientation for Printing Both Sides of Paper
The duplexer prints the second side of paper first, so paper such as
letterhead and preprinted paper needs to be oriented as shown in
Figure 8.
Figure 8 Paper Orientation for Printing Both Sides of Paper
For Tray 1, load the first side facing down and the top toward you.
For all other trays, load the first side facing up and the top toward
the printer.