Directly from an open document you can create a task and see tasks already linked to the document – ideal for attaching to-dos or deadlines to a specific document.
How to do it
Open the document in the viewer and click Tasks in the toolbar. A list of the tasks already linked to the document opens – with due date, last change, assignees and status.

Use Create task to add a new task that is automatically linked to this document. How to manage tasks in general is shown in Managing tasks.
