SignRequest offers the option to add an extra layer of security by requesting the signer to add a one time password code during signing. In this case not only the email address is verified, but also the mobile phone number of the signer.
To add a text message verification:
1. Follow the usual steps of uploading a document and adding the user(s) that need to sign.
2. Click the 'Advanced' button (Below the 'Contacts' field).
3. In the dropdown you can now add a mobile phone number to the signer(s) of your choosing.
Please note that an additional fee applies per sent text message (0.20 USD) and a paid subscription is needed.