What is a good document signing app?

So I work for a doctor and I have been fruitless on convincing them to buy Surfaces for their practice because I can’t prove much as far as usefulness when it comes to them and I can’t get a “loaner” for them to test out. So my thinking was that We get an app for either one of our already touch screen laptops, or an old Samsung android tablet.

This app doesn’t necessarily need to be free, however getting trial app with unlimited accessibility until the trial is over.

If anyone has any suggestions, that would be very much appreciated!