The track changes feature is available for all non-pdf documents in Propdocs. By default, track changes is disabled for a document that is created from a template or from blank. Documents created by uploading a word document have track changes enabled by default.
Track changes can be enabled and disabled when the document is in the Draft status using the track changes toolbar item:
When a document is in the draft status, track changes can be enabled/disabled by your teammates with Edit permissions. When you close a Draft document, track changes will remain enabled or disabled (depending on where you left it when you closed the document) for the next teammate who opens the document.
When a document is sent for review to the counterparty, the track changes will be enabled and cannot be disabled by any party. In addition, any changes made by your counterparty will require approval by your team, and cannot be approved by the counterparty (no-one can approve their own changes).