How to Add Comments to a PDF Online or on Any Device

Q: Q1: Can other people see the comments I add to a PDF?

Yes, if the comments are saved in the PDF. Send the reviewed copy rather than the untouched original, and test it in another standards-compatible reader. Comments left only in a cloud review may require the recipient to open the shared review link.

Q: Q2: Do PDF comments change the original text?

No, comments do not rewrite the source text. They are annotation objects placed above the page. Use editing tools only after a suggested correction has been approved and you have permission to modify the document.

Q: Q3: Why can I not comment on a PDF?

The file or sharing permission may block comments. Check whether the PDF has security restrictions, whether the shared link grants commenting access, and whether the document has been signed. Ask the owner for a review-enabled copy instead of bypassing protection.

Enola Miller

Home » Annotate PDF » How to Add Comments to a PDF Online or on Any Device

Quick Answer:

To add comments to a PDF, open the file in a PDF annotator, choose a comment tool such as a sticky note, text box, or highlight, place the comment beside the relevant content, and save the PDF. UPDF provides these tools on Windows, Mac, iPhone, iPad, and Android, while a browser editor works for occasional online reviews.

Comments sit on top of a PDF as annotations; they do not rewrite the document's original text. That distinction matters during a review: use a comment to suggest a correction, but use a PDF editor when you have permission to make the correction itself.

For repeat reviews or files that should stay on your device, download UPDF and open the PDF locally. For a one-off file already shared in a browser, an online review tool may be the shorter route.

Part 1: Which PDF Commenting Method Should You Use?

Choose the path based on where the PDF is stored and what the recipient needs to do with your feedback.

Your situation	Recommended method	Why	Main limitation
You review PDFs regularly on Windows or Mac	UPDF desktop	Full comment and markup set; the file can stay local	Requires installing an app
You need to comment while traveling	UPDF for iOS or Android	Adds notes and markup directly from a phone or tablet	A small screen is slower for dense reviews
The PDF is already in a browser-based review	Adobe Acrobat online	Convenient for shared comments and replies	Uploads the file and may require sign-in
You only need one simple note on a Mac	Preview	Already included with macOS	Fewer review and comment-management options
You need to correct the actual document	PDF editing, not commenting	Changes the source text or image directly	Requires edit permission and may affect layout

Part 2: How to Add Comments to a PDF on Windows or Mac with UPDF

UPDF allows you to edit all elements within a PDF, including text. Whether you need to delete, modify existing text, or add new text, UPDF can handle it all. As a powerful PDF editor, it ensures a smooth editing experience without altering the original formatting. Download UPDF here and follow the guide below to add comments in your PDF.

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click Tools > Comment.
Now, click the Text Comment option from the annotation bar at the top.
Click anywhere in the PDF to add the text box and begin typing.
Choose the style for the text, including the font color, size, and type, from the floating bar at the top.

UPDF is useful when you want to review locally and keep several comment styles in one workflow. Download UPDF for free to add comments to your PDF — installation is free, and Pro removes the trial watermark from exported files.

Part 3: How to Add Comments to a PDF on Mobile

UPDF is a powerful iOS application that allows users to annotate and sign PDF documents on their iOS mobile devices efficiently. Combined with the ability to import files from diverse sources, this effectively gives you complete mobility to handle any document workflow easily from your iPhone or iPad. If you want to try it, click the download button below.

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Tap the Comment Icon on the bottom-left corner of the screen.

Below, you'll see a banner displaying all annotating tools. You can select from highlight, strikethrough, underline, and squiggly line.

Tap any of the icons, the default color effects will be displayed next to these tools. To change the color, click the color icon next to the corresponding tool and you can view a detailed screen of that markup tool.
You can then adjust the opacity and color according to your preference.

Apply the annotations to your document and save your changes.

The Comment area also contains highlight, strikethrough, underline, and squiggly tools.

Part 4: How to Add Comments to a PDF Online for Free

Adobe Reader solves the top 3 user pain points of free online tools: no mandatory export watermarks, full cross-PDF compatibility for editable comments, trusted secure cloud storage, and complete basic annotation types without overly strict file quotas. Perfect for casual, cross-device PDF commenting for non-confidential work.

An online editor is practical for one non-sensitive review. Adobe states that its online PDF editor can add comments and markups in a browser.

Open Adobe Acrobat Online in any browser, upload your target PDF file
Locate the Comment toolbar on the right sidebar
Select desired comment type: Sticky Note, Highlight, Callout, Stamp, Shapes
Click anywhere on the PDF page to place markup, type your feedback text
Use the reply icon under existing comments to start team discussion threads
Click Download → Export PDF; no watermark saved to local device

FAQS

Q1: Can other people see the comments I add to a PDF?

Yes, if the comments are saved in the PDF. Send the reviewed copy rather than the untouched original, and test it in another standards-compatible reader. Comments left only in a cloud review may require the recipient to open the shared review link.

Q2: Do PDF comments change the original text?

No, comments do not rewrite the source text. They are annotation objects placed above the page. Use editing tools only after a suggested correction has been approved and you have permission to modify the document.

Q3: Why can I not comment on a PDF?

The file or sharing permission may block comments. Check whether the PDF has security restrictions, whether the shared link grants commenting access, and whether the document has been signed. Ask the owner for a review-enabled copy instead of bypassing protection.

Conclusion

The right way to add comments to a PDF depends on where the file lives and what happens after the review. UPDF is the strongest fit for repeat local work on Web, or Online; a browser editor is convenient for an occasional online review. Whichever method you choose, save a separate reviewed copy and test the comments before sending it.

For one consistent commenting workflow across desktop and mobile, Download UPDF for free to add notes, callouts, text boxes, and markup to your PDF — installation is free, and Pro removes the trial watermark from exported files.

Windows • macOS • iOS • Android 100% secure

Enola Miller

Staff Editor

Enola Miller is a staff editor specializing in PDF-related content. With over six years of experience working with PDF software, she has developed a comprehensive understanding of the common issues and needs that users encounter. She is passionate about sharing her knowledge and is always eager to provide helpful tips to assist readers in navigating the complexities of PDF documents.