HP Color LaserJet Enterprise CM4540 MFP series - Manual (Page 209)

Copy on both sides (duplex)
1. Load the original documents into the document
feeder with the first page facing up, and with
the top of the page leading.
2. On the control panel, touch the Copy button.
3. Touch the Sides button.
4. To make a two-sided copy from a one-sided
original, touch the 1-sided original, 2-sided
output button.
To make a two-sided copy from a two-sided
original, touch the 2-sided original, 2-sided
output button.
To make a one-sided copy from a two-sided
original, touch the 2-sided original, 1-sided
output button.
Touch the OK button.
5. Touch the Start button.
ENWW Copy on both sides (duplex) 189