Marking up documents allows you to indicate desired text changes that can be accepted or rejected or commented by others when editing a document collaboratively.
The Markup tool appears at Comment > Annotate > Active Markup.
This multi-purpose tool lets you indicate places where you suggest text should be deleted, inserted or replaced. Its drop down list offers the following:
Text Markup tool – select this to begin.
Insert text at cursor
Replace selected text
Add note to selected text
Highlight selected text
Underline selected text
Cross out text for deletion
Marking up can be paused or terminated by clicking the Hand tool.
The topic Markup Tools describes the use of each item in detail and shows illustrations of the display results.