I work for a horse veterinarian, and I fill out and file paper invoices and carbon copies for him. Naturally, this can be difficult. I'm wondering if there's a way to save stress and money by using a program to store information about clients and type up and print invoices. (He is a mobile vet working out of his truck, so he'd be using a local wireless printer to print them if such a thing exists.) I'd like something with a good UI, something that someone with average computer literacy can understand.