The default behavior when a Form template is changed, is that the change applies to all forms, even those already created and filled in.
In a quality environment, you probably do not want this to happen, as you need to guarantee that a Form that has been completed is not changed. If you want to change a template, you should therefore create another Template with a revision name. Note that you can easily duplicate a Template from your web account.
You could also use Groups to classify the templates based on revision state. Example: a group named “Current Revisions” and another group named “Archived Revisions”. This will make it easier for users to identify the revision to be used when creating a new Form.
Finally you could activate the PDF Archive Email option: A PDF export of each Form will automatically be sent to this email when it reaches its final state, e.g. Submitted or other states if a Workflow is defined.
This will ensure you store a copy of each Form exactly as it was when it was completed.