Once a Task WIN document has been marked up, the marked up is visible from the WIN Operation that a mark up exists. 

The mark up can be viewed within the job step for updates and to approve or reject the mark up comment. The red pen icon will be displayed if there is a red pen outstanding. A task author will have received a notification that a red pen mark up has been made.

See the following to view and approve a red pen mark up comment. Comments can be made when approving or rejecting. These comments

NOTE: use SHIFT+F5 to refresh a Task WIN if the comment isn't visible.