Choose the highlighter tool and then select the text. You can also first select the text and then click the highlighter tool.
Deleting Highlights
Click on the highlighted text and then click the trash icon.
Adding Comments
Click the + button next to your highlight to add a comment. Highlights with a comment will have an outline on them
Using Emojis
Add emojis to your comments by clicking on the emoji button in the comments section
Changing Color
Change the color of your highlights by clicking on the paintbrush icon next to your highlight. Click to cycle through possible colors.