HP Officejet Pro 251dw Printer series - Manual (Page 23)

2. Insert the media print-side down in the center of the tray. Make sure the stack of
media aligns with the line on the width guide, and is not higher than the paper
stack line on the guide.
NOTE: Do not load paper while the printer is printing.
3. Slide the paper guides in the tray to adjust them for the media size that you have
loaded, and then reinsert the tray.
4. Pull out the extension on the output tray.
Load custom-size paper
Use these instructions to load custom-size paper.
CAUTION: Use only custom-size paper that is supported by the printer. For more
information, see Paper specifications.
NOTE: Load only plain paper in Tray 2.
1. Pull out Tray 1.
2. Insert the media print-side down in the center of the tray. Make sure the stack of
media aligns with the line on the width guide, and is not higher than the paper
stack line on the guide.
NOTE: Do not load paper while the printer is printing.
Load paper 19