Do you plan to make one invitation per sheet of paper using the entire sheet? If
so, setup your card as a booklet. It would be the easiest way.
If you want two cards per sheet, setup the page as a booklet, type 4.25 width
and 5.5 height, portrait. Publisher will say it will print two booklets per
sheet.
If you want the cards to be a tent type card, rotate the front and the inside 90
degrees. Look at print preview to be sure you are rotating the correct
direction.
