PDF annotations are most useful when each mark has a clear purpose. Use highlights for passages, shapes for regions, and short notes for decisions or questions.
Pick the right markup
Avoid drawing over text when a highlight or callout would be easier to understand.
Keep feedback readable
Use a consistent color for each reviewer and keep comments specific enough that someone can act without a meeting.
Save a review copy
Keep annotations in a separate review copy until changes are approved, then archive the final document without temporary notes.