Change the margins on a number 10 envelope in word 2007

Whenever I print a #10 envelope using Word 2007, the inside address is skewed too far in from the left margin of the envelope. It is not a big disaster, but I would prefer it more on the edge of the envelope’s left side.
Is there a setting somewhere I can change the margins so they come true not only in print preview but actually printing?
I’m using an epson R380 with Windows XP Media edition and Office Pro 2007.

Any ideas? Thanks,

Joanne