Updating A Previously Approved Form

I hope I can  make this clear:

1. I have a form that has been through a workflow for approvals and the workflow has been completed. This form also has an ID assigned to it.
2. Let's say six months later there is an update to this form. The form needs to go through the workflow approvals process again, but it is important that the form retain the ID assigned to it in the first round. Note: The amount of time could be any time range, 6 months, 2 years, 5 years, etc.

I am working in O365. What can I do to kick this workflow off again?

I am working in O365.