Once you have added all the recipients for a document, you can choose which roles the recipients should have. Click on the text that says Signer under the recipient name and a dropdown option shows.
There are three different roles that a recipient can have; Signer, Approver, and Recipient:
Signer - A signer is a recipient who is to sign the document and thereby become legally bound to the document.
Approver - An approver is usually an internal party, such as HR, that must approve that the document is correct before proceeding with signing.
Recipient - A recipient of a document can only read the contents of the document. This means that they have no active role in a signing but only receive the document for reading. You can see it as a CC in an email.