What is the best way to get contracts signed a Windows tablet or iPad?

Hi,

I have a customer in the building business.  I have set up and/or fixed his network and several computers over the last few years.  He is trying to figure out what the best combination of documents type and touchscreen device to create, edit, and show a job order to a customer and have them sign off.  He does this with paper right now but it causes delays and related problems since he often can't create or edit an order on site.

So I guess I'd like to get some pointers to existing schemas for using tablets with what programs or document types, etc.   I've been looking around and I'm not seeing anything that exactly works for this.  But I'm guessing this is ground that's been well established.  Anyone have any ideas?

I'm also open to suggestions as to what category this should have been placed in.

Thanks for any help!!