What to do when a voucher might not be the right present?

I'm thinking about giving a voucher for a massage to a female friend of mine due to her stressful job, but since it's quite expensive, I'm now thinking about what I could do in order to avoid wasting money on that in case she wouldn't want it.

I've read that I could print the voucher out at home, but I have no experience with this. Does that mean that I have to pay for it online in advance?