Open 'Diff View & Sync' and don't adopt any items. Click 'Send' directly. Sending 0 changes is valid and means "send my original version back unchanged". The other party will receive your version and see the differences on their end. If you agree with only some changes, adopt only those and send. To add an explanation, you can write it in the 'Other Information' field and send it together, or open the 'Discussion' on the document to communicate directly with the other party (discussion is a conversation tied to the document and can include attachments). The 'AI assistant' in the diff interface can also help you draft a response strategy and suggested communication text for the other party. However, it only fills the draft—you must review it yourself before clicking send.