I also printed my wedding invitations and programs on my laser printer, using MS Word. You don't need a special program. I got matching invitation cards, reply cards, and envelopes from my local crafts store, put together a nice design, and ran them off. It's easy and relatively inexpensive, and several people remarked on how professional they looked... "oh, where did you have them done?"
If you're a good calligrapher you can do the addresses by hand (that's what I did). If not, get a calligraphy pen and just write them out in cursive - it looks great.
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