Load Envelopes You can print on plain paper or air mail envelopes in 4 1/8 × 9 1/2 inch (#10) size. 1. Open the paper support, then pull up the extension. 2. Open the front cover and pull out the tray extensions. 3. Slide the edge guide to the left. 4. Load up to 10 envelopes against the right side and beneath the tab. Load them printable side up and flap edge left. 5. Slide the edge guide to the edge of the envelopes, but not so tight that the envelope bows Tip:Press each envelope flat before loading it or load one envelope at a time. See also: Load Paper for Photos Load Paper for Documents