When you are reviewing proofs in a collection, if you find you need to add the same comments to all or several proofs in a collection, you can easily do this in a few clicks.
To add a comment to several proofs at once
Open one of the proofs in the collection, and click the collection icon at the bottom of the proofing screen.
In the collection view, click the general comment icon.
Note: By default, all the proofs in the collection will be selected, but you can deselect any proofs you do not want the comment to be added to.
Type your comment and click the send icon (or use the shortcut key shift+enter or cmd+enter).