Oki C 5400n - Manual (Page 196)

Windows: PCL Emulation Driver • 194
Printing Custom Page Sizes
2000
The printer media size for the tray you’re using must be manually set
in the driver to the custom paper size before use (range 3½'' to 8½''
[89 to 216 mm] wide x 5'' to 14'' [127 to 356 mm] long).
1. Make sure the rear exit path is open:
2. Load the custom size paper in the tray of your choice.
3. Open the file in your application and select File → Print .
4. In the Print dialog box, select the PCL printer.
NOTE
Up to 32 custom page sizes can be defined in the PCL
driver.