Click the settings gear menu in the top right corner. Select
Version history from the dropdown menu.
All published versions of a Workflow and related version information will be available to navigate on the left. When you select a version to view, you will see a preview of the Workflow version to the right. From this view only preview, you can look through the webform and PDF to determine if this is the correct version you are searching for.
Click the vertical
... more menu next to the version name you would like to restore and select
Revert to this version… from the dropdown.
Your selected version of the Workflow will not be live for submissions just yet. Confirming changes will replace any current draft of the Workflow with the selected version. You will be taken to the Workflow editor with your selected version ready for editing.
Make any further changes you wish to the Workflow draft and publish when you are ready for all current and new submissions to use this Workflow version.