Oki B 4250 - Manual (Page 44)

PAPER RECOMMENDATIONS > 44
4. Press the Value (+) or (–) button until the required paper type or
weight is displayed, then press the Select button. A plus (+)
appears next to the selected paper type or weight.
5. Press the Online button to return the printer back to online status.
Select the correct paper settings in the printer driver before printing the
file.