Hmmmm... you would have to use word and make the size of the document match the size of your envelope (3.5x5.5 or whatever) and then put your return address in the center/top of the document so it lines up with the flap of your envelope. Then just make sure you run them through the printer so the flap is the side being printed on... I would just test this first because I'm not sure of the flap would get stuck if it's going through the rollers (or whatever is inside of a printer).
If you want to print it on the back then the part with the flap needs to face down (away from you)
Yeah this is going be tricky... What if you had a stamp made with your address??? Or return labels? And just put them on the back??
