For Americans who need a postage-paid envelope to return their ballot or their ballot request/registration: I had to play around to print the envelope as given by FVAP in order for it to print correctly. Here are settings I used on my printer (Canon iP2770) that might help you in printing on an envelope (I used envelopes 11 x 23 cm) and started with an image of the FVAP one. Hopefully this helps you print a postage-paid one. If not, several of us (myself and some others in Ubud) and perhaps the Bali Consulate have some stamps you can use (all free).
Print settings I used
Envelope image used with print settings above