Epson DLQ-3500 Reference Manual page 119

Note:
Load paper with the printable side up. If you are using pre-printed
forms, load the forms top-down.
7. Push back the paper set levers to clamp the paper against the
guide rollers.
8. Before printing, make sure that Manual/CSF is selected as the
paper source on the control panel. If not, select it by pressing
the Paper Source button. Also set the paper-thickness lever
to the appropriate position for the paper loaded in the
cut-sheet feeder as described in "Adjusting the
Paper-Thickness Lever" on page 1-5. In your printer driver
software, select your paper size from the Paper Size list.
Options and Consumables
5-11