Allow customers to sign contract on my 8.1 tablet without creating digital id

I'd like to be able to have multiple people sign a contract while in the field from my Windows 8.1 tablet. How do I do this without needing to create a digital id for every single customer? The form is saved to OneDrive and all employees will download the form each time they need to use it for a new customer. Both the employee and the customer will need to sign.