Participate in a review
When you receive a PDF to review, you can annotate it by using the commenting and markup tools. You use the same tools to return your comments to the author. (These features are available only if the PDF author has enabled commenting.)
Drawing Markups panel
A. Add text box B. Add text callout C. Draw line D. Draw arrow E. Draw oval F. Draw rectangle G. Draw cloud H. Draw polygon I. Draw connected lines J. Draw free form K. Erase free form