The Annotate feature can be used to draw on the document in the Viewer. This allows you to mark up sections in a document that need to be called out.
To annotate documents:
Once you have added an annotation to a document, the document is displayed in the Documents tab with an icon indicating that there are annotations on the document.
If the document has also had notes or bookmarks added to it, an icon is displayed indicating that more than one feature has been added to the document.