A family of Microsoft word processing software products for creating web, email, and print documents.
If you have set the same printer to be the active printer in Word, then Word will display all the sizes that are available in the driver.
To set your printer as the active printer, choose File>Print in Word and choose your HP printer from the Printer dropdown. Then leave the Print backstage page and return to your document. Choose Layout>Size and select A2 envelope.