Mark It Up! Fun & Easy Ways to Add Comments to PDFs Anywhere

Adding Comments to PDFs: A Simple Guide

PDFs are one of the most popular document formats—they’re easy to share, secure, and look the same on any device. But what if you need to give feedback, highlight important points, or collaborate with others? That’s where comments come in!

Comments let you add notes, highlight sections, and provide suggestions without altering the original content. Whether you’re reviewing a report, marking up a contract, or working on a team project, commenting makes communication easier and more efficient. Instead of long email threads or separate documents, everything stays neatly inside the PDF.

So, how do you add comments? The good news is that there are multiple ways to do it—from using Adobe Acrobat’s built-in tools to free online platforms and mobile apps. No matter what device or software you have, there’s a simple way to annotate PDFs like a pro.

In this guide, we’ll walk you through different methods of adding comments using various tools. Whether you’re a student, a professional, or just someone who wants to mark up a PDF easily, you’ll find the perfect solution for your needs. Let’s get started!

Why Add Comments to PDFs?

Adding comments to PDFs is a powerful way to communicate, making collaboration and feedback more efficient. Whether you’re a student, a professional, or part of a team, commenting helps you share thoughts, highlight key points, and provide suggestions—all without changing the original document.

Who Needs to Add Comments?

Students: Mark up lecture notes, highlight important sections in study materials, or add explanations for later review.

Professionals: Provide feedback on reports, annotate contracts, or collaborate on business proposals.

Teams: Share insights, suggest revisions, and keep discussions organized within a single document.

Editors & Writers: Review manuscripts, suggest changes, and refine content with precise comments.

Benefits of Commenting on PDFs

✅ Improves Collaboration – Teams can review, suggest, and discuss changes in one place, eliminating long email chains.

✅ Enhances Feedback – Editors, teachers, and managers can provide detailed notes without modifying the original text.

✅ Boosts Productivity – No need to rewrite documents; just add, resolve, or reply to comments for faster revisions.

✅ Great for Personal Notes – Use comments for self-study, bookmarking, or reminders in important documents.

Real-World Use Cases

A professor adds explanations and suggestions to a student’s research paper.
A lawyer reviews a contract and highlights areas needing clarification.
A marketing team collaborates on a brochure design, suggesting edits directly in the PDF.
A project manager provides feedback on a proposal before finalizing it for clients.

No matter your role, commenting on PDFs makes document interaction smarter, smoother, and more effective!

The Built-In PDF Commenting Tools

Adding comments to PDFs is easy with built-in tools available in popular applications. Whether you’re using Adobe Acrobat Reader DC, Mac Preview, or Microsoft Edge, these tools let you highlight, annotate, and provide feedback directly within the document—no extra software needed!

1. Adobe Acrobat Reader DC (Windows & Mac)

Adobe Acrobat Reader DC is one of the most widely used PDF viewers, and it offers powerful commenting tools for free.

How to Add Comments in Adobe Acrobat Reader DC

1. Open your PDF in Adobe Acrobat Reader DC.

2. Click on “Comment” in the right-hand toolbar (or go to View > Tools > Comment > Open).

3. Select the desired annotation tool:

Sticky Note: Click anywhere in the document to add a comment.
Highlight: Select text and click the highlight icon.
Underline & Strikethrough: Choose text and apply markup.

4. Type your comments in the pop-up box.

5. Click Save to keep your changes.

✅ Pros:

Advanced commenting tools (highlight, underline, sticky notes, and drawing tools).
Comments are easy to reply to and resolve.
Works on both Windows and Mac.

❌ Cons:

Requires installation.
Some advanced tools are only available in the paid version (Acrobat Pro).

2. Mac Preview (For Mac Users)

Mac users can easily annotate PDFs using the built-in Preview app, which comes pre-installed on macOS.

How to Add Comments in Mac Preview

1. Open your PDF in Preview.

2. Click “View” > “Show Markup Toolbar” (if it’s not already visible).

3. Use the following tools:

Text Box: Click the “Text” icon (T) to insert comments.
Highlight: Select text and click the highlight button.
Notes: Click the “Note” icon to add a sticky note.

4. Click File > Save to keep your annotations.

✅ Pros:

No need to install additional software.
Simple and easy to use for basic annotations.

❌ Cons:

Lacks advanced commenting features (no strikethrough, underlining, or threaded comments).
Limited compatibility—not available for Windows.

3. Microsoft Edge PDF Viewer (For Windows Users)

Microsoft Edge comes with a built-in PDF reader that allows basic annotations, making it a great option for quick edits.

How to Add Comments in Microsoft Edge

1. Open the PDF in Microsoft Edge.

2. Click the pen icon on the toolbar to access annotation tools.

3. Choose:

Highlight: Select text and choose a color.
Draw: Use a stylus or mouse to write directly on the PDF.
Text Comments: Right-click and choose “Add Text”.

4. Click Save to keep your changes.

✅ Pros:

No need to install additional software.
Works directly in your browser.

❌ Cons:

Limited features (no sticky notes, no advanced commenting options).
Not ideal for professional editing.

Built-in PDF commenting tools offer a quick and convenient way to add feedback, but they vary in features. Adobe Acrobat Reader DC is the best free option for advanced comments, while Mac Preview and Microsoft Edge work well for basic annotations. If you need more advanced tools, you may need to explore third-party PDF editors!

Online Tools for Adding Comments to PDFs

If you don’t want to install software, online PDF editors offer a quick and easy way to add comments, highlight text, and annotate PDFs—all from your web browser. Whether you’re working remotely, using a shared device, or just need to make quick edits, these tools are a convenient alternative to traditional PDF software.

Best Online Tools for Adding Comments to PDFs

Several web-based PDF editors provide annotation and commenting features. Below are three of the most popular options:

Pdf4sure – Simple and user-friendly.
PDFescape – Feature-rich with free and premium versions.
Sejda – Great for quick edits with no sign-up required.

1. Pdf4sure (Easy and Intuitive)

Pdf4sure is a well-known online tool that offers a clean, user-friendly interface for annotating PDFs.

How to Add Comments in Pdf4sure:

1. Visit Pdf4sure.

2. Click “Choose File” to upload your PDF.

3. Use the Comment tool to add sticky notes or text comments.

4. Use the Highlight tool to emphasize important sections.

5. Click “Download” to save your edited PDF.

✅ Pros:

Very easy to use.
Works on any device with a browser.
No installation required.

❌ Cons:

Free version has a limited number of edits per hour.
Requires an internet connection.

2. PDFescape (Free with More Features)

PDFescape is a powerful free online PDF editor that allows commenting, highlighting, and form filling.

How to Add Comments in PDFescape:

1. Go to PDFescape.

2. Click “Free Online” and upload your PDF.

3. Select the Text tool to add comments.

4. Use the Sticky Note tool for annotations.

5. Save and download your commented PDF.

✅ Pros:

Completely free for files under 10MB.
No account required for basic features.
Offers additional tools like form filling and redaction.

❌ Cons:

Larger files require the paid version.
The interface is a bit clunky compared to other editors.

3. Sejda (Great for Quick Edits)

Sejda is another excellent online tool that provides basic commenting features without requiring sign-up.

How to Add Comments in Sejda:

1. Visit Sejda.

2. Click “Upload PDF” and select your file.

3. Choose the Annotate tool to add comments or highlights.

4. Click “Apply Changes” and download your file.

✅ Pros:

No registration required for basic edits.
Simple and fast for quick annotations.
Supports multiple annotation types (text, sticky notes, highlighting).

❌ Cons:

Free version limits documents to three edits per hour.
Cannot handle large PDF files in free mode.

When to Use Online vs. Offline Tools?

When you don’t want to install software.
When you need a quick edit on a shared or public device.
When collaborating remotely with others.
When to Use Offline Tools
When working on large files or confidential documents.
When you need advanced commenting and markup options.
When you want to work offline without internet access.

Online PDF editors like Pdf4sure, PDFescape, and Sejda make adding comments easy and accessible from any device. However, they come with limitations, such as file size restrictions and internet dependency. If you need quick annotations, these tools are perfect. But for more advanced features, offline editors like Adobe Acrobat remain the best option.

Choosing the right tool depends on your workflow, security needs, and editing frequency. Whether online or offline, commenting on PDFs has never been easier!

Adding Comments on Mobile Devices

With smartphones and tablets, commenting on PDFs is easier than ever, allowing you to review documents, add feedback, and highlight important sections on the go. Whether you’re using an iPhone, iPad, or Android device, there are several apps that make it simple to annotate PDFs right from your mobile screen.

Adding Comments on iPhone & iPad

Apple devices come with built-in tools for basic PDF annotations, and third-party apps like Adobe Acrobat offer even more features.

1. Using Apple Books (For Quick Annotations)

Apple Books (formerly iBooks) allows basic highlighting and notes directly in PDFs.

How to Add Comments in Apple Books:

1. Open the PDF in the Books app.

2. Tap and hold text to see annotation options.

3. Select Highlight or Note to add a comment.

4. Tap Done to save.

✅ Pros: Simple, no extra apps needed.

❌ Cons: Limited to basic text highlights and notes.

2. Using Adobe Acrobat (For Advanced Commenting)

Adobe Acrobat’s mobile app offers sticky notes, text comments, highlights, and markup tools.

How to Add Comments in Adobe Acrobat on iPhone/iPad:

1. Open the PDF in the Adobe Acrobat app.

2. Tap the comment icon (speech bubble).

3. Select an annotation tool (Sticky Note, Highlight, Underline, Strikethrough).

4. Add your comment and tap Save.

✅ Pros: Full-featured annotation tools, cloud sync.

❌ Cons: Some features require a paid subscription.

3. Using Third-Party Apps (Good Alternatives)

Apps like PDF Expert and GoodNotes offer even more annotation features.

✅ Pros: Best for users who need advanced PDF editing and organization.

❌ Cons: May require a one-time purchase or subscription.

Adding Comments on Android

Android users have several powerful PDF annotation apps, including Adobe Acrobat and Xodo.

1. Using Adobe Acrobat (Most Popular Option)

Adobe Acrobat’s Android app works the same way as on iPhone.

Steps:

1. Open the PDF in Adobe Acrobat.

2. Tap the comment icon to add annotations.

3. Choose between Sticky Notes, Highlights, and Text Edits.

4. Save and share the annotated PDF.

✅ Pros: Free for basic commenting, widely used.

❌ Cons: Requires an account for cloud sync.

2. Using Xodo (Best Free Alternative)

Xodo is a feature-rich, free PDF editor for Android.

How to Add Comments in Xodo:

1. Open the PDF in Xodo.

2. Tap the annotation toolbar.

3. Use Sticky Notes, Freehand Drawing, or Text Comments.

4. Save and export the document.

✅ Pros: 100% free, no sign-up needed, great for collaboration.

❌ Cons: Interface may feel overwhelming for new users.

Whether you’re using an iPhone, iPad, or Android device, mobile apps provide easy ways to add comments to PDFs. If you need basic annotations, Apple Books or Xodo are great choices. For advanced commenting, Adobe Acrobat remains the top pick across all platforms.

Need more features? Consider third-party apps like PDF Expert (iOS) or Xodo (Android). No matter your device, you can now review and comment on PDFs from anywhere!

Advanced Commenting Features in PDFs

Beyond simple text comments, many PDF tools offer advanced annotation features that make collaboration and feedback even more effective. Whether you’re highlighting key points, adding voice comments, or drawing annotations, these features help you communicate more clearly and efficiently.

1. Highlighting and Underlining Text

Highlighting and underlining are essential tools for reviewing documents. They help draw attention to important sections and make it easier to navigate long PDFs.

How to Highlight or Underline in Adobe Acrobat:

1. Open your PDF in Adobe Acrobat Reader.

2. Select the Highlight tool or Underline tool from the toolbar.

3. Drag over the text you want to emphasize.

4. Click on the highlighted text to add a comment (optional).

✅ Best For: Reviewing documents, studying, editing drafts.

❌ Limitations: Doesn’t provide detailed feedback without adding comments.

2. Adding Sticky Notes and Pop-Up Comments

Sticky notes are digital Post-it notes that allow you to add detailed feedback anywhere in the document. When clicked, they expand into pop-up comments for easy reading.

How to Add Sticky Notes in PDF Editors:

1. Open your PDF in Adobe Acrobat, Xodo, or Pdf4sure.

2. Click the Comment tool → Select Sticky Note.

3. Click anywhere on the page to place the note.

4. Type your comment and save.

✅ Best For: Collaborative feedback, document reviews, peer editing.

❌ Limitations: Too many sticky notes can clutter the document.

3. Drawing and Freehand Annotations

For more visual feedback, many PDF tools allow freehand drawing and shape annotations. This is useful for:

Marking up diagrams and charts.
Circling or underlining key points manually.
Sketching quick explanations.

How to Use Freehand Drawing Tools:

1. Open your PDF in Adobe Acrobat, Xodo, or PDF Expert.

2. Select the Freehand Drawing or Pen tool.

3. Draw directly on the document using a stylus or finger.

4. Adjust color, thickness, or opacity if needed.

✅ Best For: Annotating PDFs on touchscreen devices, marking up visual elements.

❌ Limitations: Handwritten notes can be messy or hard to read.

4. Voice Comments (Audio Annotations)

Some advanced PDF editors let you record voice comments, making it easier to provide detailed feedback without typing.

How to Add Voice Comments in Adobe Acrobat Pro:

1. Open your PDF and go to Tools > Comment.

2. Click the Attach File tool and select Record Audio.

3. Speak into your microphone and save the file.

✅ Best For: Giving verbal feedback, explaining complex ideas, accessibility.

❌ Limitations: Not all PDF viewers support audio comments.

Advanced commenting features enhance collaboration and document review, making PDFs more interactive and easier to navigate. Whether you prefer text-based annotations, visual markups, or voice feedback, there’s a tool for every need. Try combining multiple features for the best reviewing experience!

Pro Tips for Effective PDF Commenting

Adding comments to PDFs is easy, but making them clear, organized, and effective takes a little strategy. Whether you’re reviewing a document solo or collaborating with a team, structured commenting can save time and reduce confusion. Here’s how to make the most of PDF annotations.

1. Keep Comments Organized and Readable

Messy or excessive comments can make a document harder to review than no comments at all! To ensure clarity:

Be concise. Keep feedback short and to the point.
Use proper grammar and punctuation. This makes comments easier to understand.
Avoid overlapping comments. Place sticky notes where they don’t block important text.

✅ Best Practice: If commenting on multiple sections, number your comments for easy reference.

2. Use Color-Coding and Labeling for Clarity

Colors can help categorize feedback, making it easier for reviewers to scan and process.

Color-Coding Examples:

Yellow = General feedback (clarifications, minor edits).
Red = Critical issues (errors, necessary changes).
Green = Positive notes (praise, well-done sections).
Blue = Questions (requests for clarification).

✅ Best Practice: If collaborating in a team, agree on a color-coding system beforehand.

3. Comment Efficiently for Teamwork and Collaboration

When working on a shared PDF, efficient commenting ensures everyone stays on the same page.
Tag team members (in apps that support it) so they know which comments need their attention.
Reply to existing comments instead of adding new ones, keeping discussions organized.
Use clear action words like “Revise,” “Clarify,” or “Reword” to avoid vague feedback.

✅ Best Practice: Group similar comments together to prevent scattered feedback.

4. Exporting and Sharing Commented PDFs

After adding comments, you’ll often need to share your annotated PDF with others. Some tools allow exporting comments separately for easier review.

How to Export Comments in Adobe Acrobat:

1. Open the commented PDF in Adobe Acrobat.

2. Go to Comments List > Options > Export Comments.

3. Save as a separate comments file or flatten annotations into the PDF.

Sharing Tips:

Use cloud storage (Google Drive, Dropbox) for easy access.
Send PDFs as attachments with a brief explanation of the comments.
Lock or flatten comments if you don’t want them to be edited.

✅ Best Practice: If multiple people are commenting, review and consolidate comments before finalizing the document.

Effective PDF commenting saves time, enhances collaboration, and makes document reviews smoother. By organizing comments, using color codes, collaborating efficiently, and sharing themyour feedback is clear and actionable. Try these pro tips and make your next PDF review process seamless!

Common Issues & How to Fix Them

Even with the best tools, you might run into commenting issues when working with PDFs. Here are some common problems and how to resolve them.

1. Comments Not Saving?

Possible Causes:

Using a PDF viewer that doesn’t support comments (e.g., browsers like Chrome).
Forgetting to save the document before closing it.
The PDF is set to read-only mode or is opened in a restricted environment.

Fixes:

✅ Always use a dedicated PDF editor like Adobe Acrobat, Foxit, or PDF-XChange.

✅ Click File > Save As to ensure comments are embedded.

✅ If using a cloud service (Google Drive, OneDrive), make sure changes are syncing properly.

2. Compatibility Issues Between Different PDF Readers

What Happens?

Comments made in one tool don’t appear in another.
Formatting of comments looks different or becomes misaligned.

Fixes:

✅ Stick to widely supported formats (Adobe Acrobat, Foxit).

✅ If sending to someone using a different tool, export comments separately (Adobe Acrobat allows this).

✅ Flatten annotations if you don’t need others to edit them.

3. Commenting Restrictions on Secured PDFs

Some PDFs are locked or restricted, preventing you from adding comments.

Fixes:

✅ Check if commenting is allowed: Go to File > Properties > Security.

✅ If you own the file, remove security settings in Adobe Acrobat (if permitted).

✅ If it’s a form, enable fillable fields to add text-based comments.

Conclusion

Commenting on PDFs is a powerful tool for collaboration, note-taking, and document reviews. From built-in tools like Adobe Acrobat and Mac Preview to online platforms and mobile apps, there are plenty of ways to annotate your PDFs efficiently.

To avoid common issues, always use a reliable PDF editor, save your comments properly, and check file permissions before editing. Whether you’re a student, professional, or editor, these commenting techniques will make your workflow smoother and more effective.

Now, it’s time to try different methods and find what works best for you!