HP LaserJet M1319f Multifunction Printer - Manual (Page 40)

4. After one side has been printed, remove the remaining media from the input tray, and set it aside
until after you finish the duplexing job.
5. Without changing the orientation, remove the printed stack from the output bin, and then straighten
the stack.
6. Maintaining the same orientation, place the stack of media in the input tray again. The printed side
should be facing down.
7. On the product control panel, press OK and wait for the second side to print.
30 Chapter 4 Use the product with Macintosh ENWW