Welcome to the forums.
I do use a Surface Pro for my own business, but since my work is mainly online only, it is considerably different from what you are asking. However, my wife's pharmacy uses a Windows 8 tablet for customers to sign for their meds. They were using an iPad for a while, but for some reason they are now using a Windows 8 solution.
Unfortunately I haven't seen it in action yet though. They recently switched and the last time I was there, the Win8 system was "not working".
With the iPad, they were using a phone connected to it (VOIP) to enable people to talk to a pharmacist, and when signing for the meds, it basically showed the different side effects that had to be checked off by the customer.
The system itself is not thought out though. The customer base of the pharmacy consists of a lot of elderly people, and just to see the look on their faces when the iPad is pushed towards them to sign in the meds makes you ask why that thing was there. On top of that, about half the people that visit the pharmacy are not proficient with the English language, and the iPad app was English-only.
If you are considering using technology such as the Surface Pro to assist you with your business, make sure that you make it work for you, but don't try to make it do your job. With signing documents, make sure that it works. If you use some sort of direct submission of signed documents or web-apps of some sort, keep in mind that you don't always have internet access, so always have a backup solution available.