There are several options for annotating a document. They are listed below.
Add a comment 
Find out here how to add a comment.
Add text 
Find out here how to add text.
Draw on a document 
Find out here how to draw on a document.
Add a shape 
Find out here how to add a shape.
Add an image 
Find out here how to add an image.
Highlight text 
Find out here how to highlight text.
Add a signature 
Find out here how to add a signature.
Manipulate a signature
Find out here how to manipulate a signature.
Tip: To save edits or annotations, just click anywhere in the document.
Don’t forget that all your annotations are displayed in the panel to the left of the document under 'Notes' 
See Lumin keyboard shortcuts here to learn how to access your tools at the touch of your fingertips.