​​How to Add Comments and Annotations to a PDF

PDFs are widely used across industries for sharing documents because they preserve formatting and are easy to view across devices. However, PDFs are not just for reading, they’re also an essential medium for collaborative review. Adding comments and annotations to a PDF enables teams to share feedback, mark up changes, and improve document accuracy and quality. Whether you're editing a contract, reviewing a design draft, or giving feedback on a research paper, PDF annotations make remote collaboration clearer and more effective.

Types of Comments and Annotations to Add to a PDF

Using a modern online PDF editor offers a wide variety of annotation tools that allow users to customize how they give feedback. Each serves a different purpose, depending on the type of comment or revision needed.

Text Comments

Text comments, or "comment boxes," allow users to type on a PDF and write detailed notes in the margin or directly linked to a specific part of the document. These are useful for contextual explanations, suggestions, or posing questions for collaborators.

Highlights

Highlighting text draws attention to specific parts of the content without making changes. This is ideal when you want to flag a passage for review, emphasize key information, or mark errors for correction.

Underlines and Strikethroughs

Underlines can be used to emphasize text or indicate that something should be bolded or revised. Strikethroughs show what text should be removed, making them valuable for proofreading and editing tasks.

Sticky Notes

Sticky notes allow users to "pin" a small note to a specific area of the document. These are often used for quick feedback, such as "double-check this statistic" or "need citation here."

Drawing Tools (Shapes and Freehand)

Shapes like rectangles, circles, arrows, and lines can be added to draw attention to a visual area of the document. Freehand drawing allows for custom markups, useful in design reviews or annotating diagrams.

Each type of annotation offers a different method of communication, and often they’re used in combination to provide a full review.

How to Add Comments to a PDF Using DocFly

DocFly is a user-friendly, cloud-based PDF editor that allows you to annotate PDFs without the need to install software. Here’s how to use DocFly to add comments and annotations:

Step 1: Upload Your PDF

Go to DocFly.com and click the “Upload PDF” button. You can drag and drop the file or select it from your device. DocFly also supports importing from cloud storage platforms like Google Drive and Dropbox.

Step 2: Open the Editor

Once uploaded, select the “Edit” option to open your PDF in the editor interface. DocFly will load the file and present various editing and annotation tools on the sidebar.

Step 3: Choose Your Annotation Tool

Click on the “Editor” tab to see your annotation options. You can choose to highlight text, add text, underline, strikethrough, or draw shapes.

Step 4: Add Your Comments or Highlights

Click on the area of the PDF you want to annotate. For example, if you're adding a comment, click the text icon and then click the relevant section of the document. A text box will appear where you can type your note. To highlight, simply click the highlight icon and select the text.

Step 5: Save and Download

Once you’ve finished annotating the document, click “Save” and choose to download the file to your device. Your annotations will remain embedded in the PDF for future viewing or further editing.

Tools for Adding Comments to PDFs

There are many tools—both online and offline—that allow users to annotate PDFs with ease. Here’s a look at some of the most popular:

Adobe Acrobat Reader DC

Adobe’s free Reader allows basic annotation features like highlights and comments. The Pro version expands these capabilities with form editing, signature tools, and advanced collaboration.

DocFly

DocFly is a lightweight, browser-based solution perfect for users who want to avoid downloading bulky software. It offers all the essential annotation features needed for quick edits and feedback.

PDFescape

This web-based tool offers annotation, form-filling, and simple editing for free. Great for occasional use or quick document markups.

Preview (Mac)

If you’re using a Mac, the Preview app comes built-in and supports annotations like highlights, text boxes, and shapes. It’s a simple but effective tool for personal or professional use.

Best Practices for Adding Comments to PDFs

Adding comments to PDFs isn’t just about using the right tools—it’s also about using them effectively. Here are some best practices for making your feedback useful and professional:

Be Clear and Concise

Avoid vague comments like “fix this” or “unclear.” Instead, be specific: “Consider rephrasing this sentence for clarity” or “Typo: change ‘their’ to ‘there’.”

Use Appropriate Annotation Types

Match your annotation tool to the feedback. Use highlights for general emphasis, sticky notes for quick tips, and text comments for more detailed explanations.

Structure Feedback Logically

If you’re reviewing a large document, number your comments or group them by section. This helps the author process and address your feedback more easily.

Customize Annotation Settings

Most tools allow you to change comment colors, fonts, and opacity. Use color coding to indicate priority or categories—for example, red for errors, yellow for suggestions.

Manage and Resolve Comments

Some tools (like Adobe Acrobat Pro) allow threaded comments and resolution tracking. If you're in a team environment, mark comments as "resolved" after they're addressed to avoid confusion.

Avoid Over-Annotation

Don’t overwhelm the document with too many comments. Prioritize major issues or sections where feedback is most necessary. Too many notes can dilute the impact of your suggestions.

Conclusion

Adding comments and annotations to PDFs is a great way to collaborate, provide feedback, and improve the quality of documents in any professional or academic setting. Whether you want to edit a locked PDF, highlight errors, suggest edits, edit a signed PDF or review complex materials, annotations help clarify your message and enhance collaboration.

With tools like DocFly, Adobe Acrobat, and other PDF editors, adding comments has never been easier or more accessible. By understanding the types of annotations available and following best practices, you can ensure your input is clear, organized, and constructive. So, next time you’re working with a PDF, don’t just read it - engage with it and help to make it better.