Yes. You can do that in the contacts page as follows:
1. Go to the contacts page from the side menu
2. Click on Add new contact ot "+" button to add the contacts
3. Fill in the contact info (please note that only first name, last name and email address are mandatory fields to save the contact)
4. To use the save contact, upload your document
5. In the signers page, start typing the name of your signer
6. Select your signer from the contacts suggestions drop down that is shown below the name field
7. The name and email address of the signer will be autofilled once a contact is selected