Add a note
“Comments” include notes, highlighting, and any other markup that you add to a PDF document. A note is the most commonly used comment.
1.		To display the Commenting toolbar, right-click (Windows) or Control-click (Mac OS) the toolbar area, and make sure that Commenting is selected.
2.		Click the Note Tool .
3.		Click in the document where you want to add a note comment, and then type your comment in the pop-up window.
4.		After you type the note, click the close box in the pop-up window, or click anywhere outside the pop-up window to leave it open.
You may also want to:
Select, move, and delete comments
Review and Comment Topics
Adding note comments in complete Help