Adding comments to a PDF lets you annotate documents for review, leave feedback for colleagues, or note questions while reading — without altering the underlying content. Comments stay separate from the document text and can be shown, hidden, or replied to.
Types of PDF Comments
PDF annotation tools typically offer several comment types. Sticky notes (text comment bubbles) are the most common — they appear as small icons on the page that expand when clicked to show the comment text. Text markup comments include highlight, underline, and strikethrough, often with an attached note. Drawing annotations let you add arrows, shapes, or freehand marks. Each type serves a different purpose in a review workflow.
How to Add Comments in Adobe Acrobat Reader
Adobe Acrobat Reader (free) supports adding sticky note comments. Open the PDF and go to Tools > Comment. Click the sticky note icon in the toolbar, then click anywhere on the page to place it. Type your comment in the note box that appears. You can move the note icon, reply to existing comments, and mark comments as resolved — useful during collaborative review cycles.
Acrobat Reader also lets you add text markup comments: select text on the page, right-click, and choose Add Note to Highlight (or Underline, or Strikethrough). The markup and note are linked so readers can see which text each comment refers to.
Adding Comments in a Browser-Based Tool
WukongPDF's PDF Editor includes a comment and annotation panel. Upload the PDF, select the sticky note or text comment tool from the toolbar, and click on the page where you want to place it. Type your note, position it, and download the annotated PDF. The comments are embedded in the file and visible to anyone who opens it in a standard PDF viewer.
This is convenient for adding comments on the go or when reviewing a document on a device without a dedicated PDF app installed.
Adding Comments on iPhone and iPad
In the Files app on iOS, open the PDF and tap the Markup icon (pencil tip). Tap the + button to add a Text comment, which places a sticky note on the page. You can also use the drawing tools to add freehand annotations. Tap Done to save the comments into the file.
Adobe Acrobat for iOS offers more comment types than the built-in Markup tool, including text markup linked to specific words and threaded reply comments — better for structured document review.
Sharing a Commented PDF and Managing Feedback
Once comments are added, share the PDF as usual — the comments travel with the file. Recipients can read, reply to, and resolve comments in any full-featured PDF viewer. In Acrobat, go to View > Comment > Comments List to see all annotations in one panel, which makes it easier to work through feedback systematically.
When the review is complete and comments are resolved, use a PDF Editor to flatten the document — this merges the annotations into the page content permanently, producing a clean final version without interactive comment elements. Alternatively, delete all comments before flattening if you don't want them visible in the final file.