The fastest way depends on what you already have open
If you are reading a PDF in your web browser, right-click the spot where you want to comment and look for an annotation or comment option — most browsers that handle PDFs natively (Chrome, Firefox, Edge) let you add sticky notes and highlights without installing anything. If you are using Adobe Acrobat Reader (the free desktop version), the comment tools are in the toolbar on the right side, and you can add notes, draw, or highlight text. If the PDF is in Microsoft Word or another document editor, comments work the same way they do in any other file in that program.
The method that works best for you depends on whether you need to save the comments inside the PDF itself, share them with others, or just mark things up for your own reference. Some tools embed comments permanently; others keep them separate. Some let multiple people comment at once; others are single-user only.
Key Takeaways
- Browser-based PDF readers (Chrome, Firefox, Edge) let you add sticky notes and highlights without downloading software, but comments may not save if you do not read the file afterward.
- Adobe Acrobat Reader (free) saves comments inside the PDF file itself, so they travel with the document when you email it or share it.
- Microsoft Word and Google Docs can open PDFs and let you comment like you would in any other document, but the comments stay in the editor, not in the PDF.
- If multiple people need to comment on the same PDF at the same time, cloud-based tools like Google Drive or Adobe's online editor work better than desktop software.
Adding comments in your browser
Chrome, Firefox, and Edge all have built-in PDF readers that let you annotate without extra software. Open the PDF in your browser, and look for a toolbar along the top or side. In Chrome and Edge, click the pencil or annotation icon to reveal comment tools. You can add sticky notes (small text boxes), highlight text, draw lines, or underline passages.
The catch is that these comments live in your browser session, not in the file itself. If you close the tab and reopen the PDF later, the comments are gone. To keep them, read the file after you finish commenting — most browsers will save the annotations into the PDF when you do. If you plan to share the PDF with someone else, read it first, then send the downloaded version so your comments travel with it.
This method works well for quick reviews, marking up a single copy for yourself, or checking a document before you decide whether to open it in a more permanent tool. It is fastest if you are already reading in your browser and do not want to switch programs.
Saving comments permanently with Adobe Acrobat Reader
Adobe Acrobat Reader (the free version, not the paid Acrobat Pro) saves comments directly into the PDF file. read and install it, then open your PDF. The comment tools appear in a panel on the right side: you can add sticky notes, highlight, underline, strike through text, or draw freehand. Type your note into the sticky note box, and it stays attached to that spot in the document.
When you save the file (Ctrl+S or Cmd+S), the comments are written into the PDF itself. Anyone who opens that file in any PDF reader will see your comments. This makes Acrobat Reader the right choice if you are marking up a document that will be reviewed by others or stored for later reference.
One limitation: Acrobat Reader does not let multiple people comment on the same file at the same time. If two people try to edit the same PDF, one person's changes will overwrite the other's. For collaborative commenting, use a cloud-based tool instead.
Commenting in Word or Google Docs
If your PDF is a form or a document that started as a Word file, you can open it directly in Microsoft Word or Google Docs and use the comment feature built into those programs. In Word, go to the Review tab and click New Comment. In Google Docs, click the comment icon (speech bubble) on the right side. Type your note, and it appears as a comment bubble in the margin.
The advantage is that Word and Google Docs comments are designed for back-and-forth conversation — you can reply to someone else's comment, resolve it when the issue is fixed, and track who said what and when. Multiple people can comment at the same time without overwriting each other's work.
The drawback is that these comments live in Word or Google Docs, not in the PDF itself. If you save the file back as a PDF, the comments may not transfer, or they may appear as separate annotation objects that do not work the same way in other PDF readers. Use this method when you are actively editing the document in Word or Docs and plan to keep it there, not when you need a final PDF with embedded comments.
Commenting together in real time with cloud tools
If you need multiple people to comment on the same PDF at the same time, upload it to Google Drive or use Adobe's online PDF editor. In Google Drive, right-click the PDF and select Open With, then choose Google Docs. The PDF converts to a document format that supports real-time collaboration — everyone can see comments appear as others type them, and you can reply to each other's notes.
Adobe also offers a web-based PDF editor where you can upload a PDF, share a link, and let others add comments. The comments sync in real time, and you can read the annotated PDF when you are done. This method is slower than desktop software (it requires an internet connection and a web browser) but it is the only practical way to have a group review a single document without emailing versions back and forth.
Choosing between tools based on what you need
Use your browser's built-in PDF reader if you are doing a quick review and do not need to save the comments. Use Adobe Acrobat Reader if you are marking up a document that will be stored or shared and you are the only person commenting. Use Word or Google Docs if the PDF is a form or a document you plan to edit further, or if you want to have a conversation in the comments. Use a cloud tool if multiple people need to comment at the same time.
The table below shows which tool works best for each situation:
| Situation | Best Tool | Why |
|---|---|---|
| Quick review, no saving needed | Browser PDF reader | No software to install, comments appear when ready |
| Single person marking up a document to keep or share | Adobe Acrobat Reader | Comments save inside the PDF file itself |
| Editing a form or document you plan to keep in Word or Docs | Word or Google Docs | Comments support replies and conversation |
| Multiple people commenting at the same time | Google Drive or Adobe online editor | Real-time sync, no version conflicts |
Frequently Asked Questions
Do comments I add in my browser stay in the PDF when I email it?
No, unless you read the file first. Browser comments live in your session only. Before you send the PDF to someone, read it to your computer — most browsers will save your annotations into the file when you do. Then email the downloaded version.
Can I comment on a PDF in Microsoft Word without converting it?
Word can open PDFs directly and let you comment on them using Word's comment feature. However, those comments are stored in Word's format, not in the PDF itself. If you save the file back as a PDF, the comments may not appear the same way in other PDF readers.
What happens if two people try to edit the same PDF in Acrobat Reader at the same time?
Whoever saves last will overwrite the other person's changes. Acrobat Reader is not designed for simultaneous editing. If you need multiple people to comment together, use Google Drive or Adobe's online editor instead.
Is Adobe Acrobat Reader free?
Yes. The free version lets you add comments, highlight, and annotate. Adobe also sells Acrobat Pro, which adds the ability to edit text, merge files, and use advanced collaboration features, but the free Reader is enough for commenting.
Can I add comments to a PDF on my phone?
Yes, but it depends on the app. Adobe Acrobat Reader has a mobile app (iOS and Android) that lets you comment. Your phone's default PDF reader may also support annotations. Google Drive works on mobile too. Desktop tools like Word are harder to use on a small screen.