How to add comments to any documents you have in P2P.
From the Tasks list:
From the document details page:
The comment is now visible on the document data in your task list and in the document workflow and history.
If you have the professional view active in Invoices and Spend plans, you can find the comment action from (More actions) > Add comment.
Note: To view the document history, click the arrow beside the comment icon in the Workflow section and click View history.