You can use the Signature Name Value Pairs to require a 'Virtual Signature Sign-Off' for a particular step.  This Name Value Pair consists of two specific configurable parameters.  

Usergroup and User can be toggled via the configuration Icon as seen in the configuration form image below.

REQUIRED TO COMPLETE STEP:

This is going to be checked true in most cases.  This will require the signature to be completed and signed off by a valid user before it can move to the next step.

USER GROUP:

To use a 'User Group', you must first have created a 'User Group' that is valid for your application.  This will allow a filtered list of users that are able to sign off the step while logged into their account.  The 'User Group' option must also be used in conjunction with 'Signature Count'.

SIGNATURE COUNT:

When used in conjuction with 'User Group', this will require that either one or more persons sign off the step (if 'Required to Complete Step' is checked true).

ALLOW REJECTED:

This option allows for the part to be signed.  If left unchecked, any type of sign off would indicate 'Approved'.

USER:

You can select a single user that is allowed to sign off the step.  Using this method can be limiting.

Sample Signature Results

Rejected - This what will be displayed on the digital Traveler should the signee hit the Reject Button.

Approved - This is what will be displayed on the digital Traveler should the signee hit the Approve Button.