To echo VoG, to how many people are you likely to give your software?
If you only have a few clients, you can use Word's own system because your clients should just get a message say "Do you trust software from Madronwell etc?" and as they know you, they can tick yes.
One word of warning, I have had problems with digital certificates. Depending on what is in your code, and which version of Word is on the machine trying to run the code, you can get major crashes. This is extremely hard to sort out and there is little information about it. I still don't know the full answer, but Word 2000 SP2 seems more stable; systems with SP1 are very flaky. If you use document variables and SP1, I can almost guarantee a crash (with or without a certificate)!
As with all software, I suggest you give it to one or two people to try before a massive distribution!! I am currenty having different problems having written code in Word 2003, I find it won't work on Word 2000 (and Access 2003, converted to 2000 won't work on 2000 etc etc etc!).
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