Set the Annotation Line Thickness
On the menu bar, click Draw.
Click the line thickness icon 
and select one of the available thicknesses.
Note
The selected thickness becomes the new default for your user account on the computer you are working on.
Select the type of annotation you want to create and draw the annotation.
To change the line thickness of an existing annotation:
Select the annotation.
Click the line thickness icon and select the thickness.
The line thickness of the selected annotation will be adjusted.