HP OfficeJet Pro X451 and X551 Series - Resize documents or print on a custom paper size with Mac

On the File menu, click the Print option.

Select the product, and then select the correct settings for the Paper Size and Orientation options.

On the File menu, click the Print option.

Open the Paper Handling menu.

In the Destination Paper Size area, click the Scale to fit paper size box, and then select the size from the drop-down list.