If you are the annotation author, or have Full Control permissions, you can delete annotations.
To delete annotations:
In a report that contains annotations, do one of the following:
Click an annotation icon, then click the Show Details icon to view the annotation in the Annotation List Panel.
Locate the Annotation List Panel at the bottom of the screen, hover over the Show panel and click it.
Highlight the annotation you want to delete, and click the Delete icon.