Lexmark Optra S1625 User Manual page 166

Using Your Printer
150
Using Print Materials
For simplex (single-sided) printing on letterhead paper, place the
printed design side face down with the top edge of the page nearest
the knob for the paper size indicator.
For duplex printing on letterhead paper, place the printed design
side face up with the top of the page nearest the length guide.
Length Guide
Knob