Used case

We have a web application developed using HTML5, Javascript, and CSS3 from which we want to sign a sales contract pdf from the end customer. It’s a responsive web application which can be used from desktop/laptop, tablet or mobile phones. We intend to use the e-signature REST API directly without using any SDK.

E-Signature possible in two ways:

1. Sales representative is face-to-face with the customer, shows the contract to the customer on his (sales representative’s) device and the customer signs. [Will be the most use method as it’s a high value sale].
2. Send an e-mail to customer to sign the contract. [Used in exceptional cases]

Questions/Requests

1. What is the appropriate authentication method to be used in this case?

Note - The sales person who will be getting the document sign to have a docusign account. preferably it should not be mandatory as in our case as sales person is a third party partner.

2. Is it mandatory for the end customer, who will be signing the document to have a DocuSign account? If NO, then how does this technically work.

Please help me. Thanks