The Comment tab contains two groups: Annotations and Comment Processing. All items presented in the Annotations group become comments and appear in the Comments panel, where they can be processed.

You can add textual comments as Notes that can be collapsed and expanded as text in a Text box or a Callout (a text box with an arrow). Existing text in the PDF can be emphasized by a highlight or underline, and text can also be crossed-out. You can also insertDrawing Objects that function as comments and accept a linked note explaining the purpose of the drawn shape. Active Markup allows proposed changes (insertions, deletions, attribute changes) to be marked for later review. Stamps placed in documents from the Stamps panel also appear as comments.

Comments do not become an integral part of the PDF, but can be replied to, commented and managed using the Comments panel. Comments can be removed by flattening a document or Removing Document Elements.