Oki C9300dn User Manual page 30

For face up printing, make sure the rear paper exit is open and
6.
the paper support is extended. Paper is stacked in reverse
order and tray capacity is approximately 100 sheets,
depending on paper weight.
Don't open or close the rear paper exit while printing as it may result in
a paper jam.
Always use the rear stacker for thick paper (card stock etc.)
Load letter headed paper face down as shown for both portrait
7.
and landscape printing:
CAUTION!
NOTE
SETTING UP > 30