To cancel a document, you may log into your AssureSign instance and find the document that should no longer be signed by using Envelope Search in the Reports section.
Once you open the detail report view of the envelope you may select "Delete this envelope" under the "Envelope Tasks" section of the report. This option will only be available if the document is in a state that allows cancellation.
A DocumentNOW Cancel method (SOAP method) is also available for cancelling documents via API using the DocumentNOW V2 APIs. A REST method /envelopes/{envelopeID}/cancel is available using the DocumentNOW V3 APIs.