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How to Add Comments in PDF

While reading a PDF document, if you want to add comments in PDF to remember while doing the revision, but don’t know how to do that, this article gives you three tools to add comments in PDF on Windows, Mac, and online. You can add highlights, sticky notes, underline, strikeout, text, stamps, and shapes to markup the important info with UPDF. Let’s dive into the details.

Part 1: Why Can’t I Add Comments in PDF?

Many users find it difficult to add comments in the PDF files for some reason. As a result, they are unable to do their quick revisions and lack comprehension of concepts quickly. Some of the reasons are:

  • There are many PDF tools that do not allow adding comments on the files automatically. Or in another case, some tools lack the feature for adding comments on PDF files directly. Due to the restriction from a particular PDF tool, you would be unable to add comments on the files consequently.
  • Another major reason is that many files limit the editing process while adding comments on them. As a result, you may enter comments on the file but would find difficulty in editing the document, such as adding pages or typing content.
  • Some tools may allow you to add comments but only in a separate copy. It means that if you want to add a comment, the tool would require you to make a copy of the file first, and then it will allow you to comment properly.

Part 2: How to Add Comments on Windows?

In this section, we will tell you how to add comments in a PDF file through the Adobe Acrobat tool for Windows users. Adobe Acrobat has a good reputation as a PDF tool as it contains advanced options and features to edit PDF documents quickly and perfectly.

Apart from adding comments through this tool, you can use various options to edit the document in accordance with your choice. The steps to insert comments in PDF on Windows are as follows:

Step 1: Launch the tool Adobe Acrobat on your computer and open its interface by clicking on it. On the left panel, click on the "My Computer" option, where you will see many options on the screen. Tap on the “Browse” button and choose the PDF file you want to import on this tool.

upload file to adobe acrobat to add comment in pdf

Step 2: After importing the PDF file on the tool, tap on the arrowhead displayed on the right panel that will open a toolbox on the screen. From the displayed options, click on the “Comment” option to continue.

add comment to pdf in adobe

Step 3: After clicking on comment, you will find options related in the below menu bar. Click on "Sticky Note" and tap on any part of the document to add a comment. On the given box, add your comment and click on "Post" to save the comment on the PDF file.

insert comment to pdf adobe

Part 3: How to Add Comments in PDF Mac?

If you are a Mac user, there is also a great choice for you to add comments in PDF. That is UPDF, a 100% free PDF annotator, which has no watermark and limitations when saving the modified file. Apart from editing your PDF document professionally through this powerful tool, you can add comments comfortably to the document with a single click.

add comment to pdf in updf

Through its exclusive features, make your comments highlighted by underlining, striking out the text, and by adding text boxes. Other distinct features of this tool that makes it extraordinary are an easy-to-use interface and responsive speed while editing. You can utilize this tool free of cost and can enjoy the editing experience in a secure environment. Hence, it’s an exceptional tool for Mac users as it offers great reliability.

Steps to Insert Comment in PDF Using UPDF

Step 1: Launch the UPDF

Begin with launching the UPDF tool on your computer and open its main interface. To import the PDF file, click on “Open File” and select the document you want to edit.

open file in updf

Step 2: Select Comment Tool

Navigate to the “Comment” icon displayed on top and click on it to open options for adding annotations.

comment button

Step 3: Add Comment to PDF

Tap on the icon of “Sticky notes” and click on a particular part of the document where you want to add the comment. Afterward, add the text on the displayed text box of sticky note and click enter to post the comment on your file quickly.

add comments to pdf

Besides this tool for Mac, if you want to learn more about other tools to add comments to PDF on mac, there are top 5 PDF annotators for Mac, making you process more opportunities to choose a proper tool.

Part 4: How to Add Comments to PDF Online?

Do you want to add comments to a PDF file through an online platform? Try using pdfFiller as an online PDF editor to insert comments in PDF without downloading any tool. pdfFiller is a popular online tool that offers several amazing options to edit and view PDF files, including the option for adding comments on the files.

Apart from adding comments on a PDF file instantly, you can also give a response to the added comments through this online tool. Keep in mind that this online tool only works for PDF files containing 150 pages or 25MB in size and not above this limit.

To add comments to PDF through pdfFiller, the steps are as follows:

Step 1: Open the tool pdfFiller online on your computer and import the file on it. On the top menu bar, click on the “Comment” option to continue.

insert comment in pdf

Step 2: On the left side, tap on the blue button showing “Add Comment” and click on any part of the document where you want to add the comment.

add comments in PDF with pdffiller

Step 3: Enter the text on the box and tap on “Save” to post the comment. For more options such as to delete, edit or reply to the comment, click on the “More” button. You can “Resolve” button to remove the comment from the PDF.

add comments to pdf pdffiller


Many students or individuals don’t know how to add comments in PDF files which may prevent them from smart learning. By adding comments or annotations, you can highlight the important text or can add essential details related to the text in the comment box. To improve your reading comprehension in PDF files, read this article to get the ultimate help. If you want to know more about other tools to insert comment in PDF, here are the best 10 PDF annotators on market, giving you more choices to choose the right tool to annotate your PDF.