CLOUD VERSION 3.2.0 - MARCH 2017
Unfortunately, the only way to change a signer in an active workflow (a workflow that has already been committed an released), is to have the incorrect user proxy the document to the correct user:
Assuming that you have allowed for proxy signing, as per:
If you set it to "No" - then the recipient at the email address you sent it to is the only person who can sign it and the document workflow will need to be redone.
If you set it to "yes" - the incorrect user can open the document in SignFlow and nominate the correct user, using the correct details:
Click Nominate someone else.
Then type the correct details here:
Click Nominate Proxy.
This will replace the existing user in the workflow with a new user.