Use the Callout tool

You can create a boxed text comment that points to a specific item by using the Callout tool. Click in the PDF document to create the text box, and then type your comments. The text box and line move independently around the anchor point, which is located at the line elbow.

Use the Hand tool to move the callout box and adjust the size. Use the Properties Bar to change the arrow or to change color, line thickness, and opacity of the box.

You may also want to:

Select, move, edit, and delete comments