You need to mark up a PDF, maybe flag a clause in a contract or color-code research citations, and you don’t want to pay for Acrobat Pro. Fair enough. I spent two weeks testing every free PDF highlighter I could find, on desktop and in the browser, and most of them are honestly mediocre. But a handful actually work well, and I’ll walk you through them below.
If you want a broader look at editing PDFs without spending money, check out our best free PDF editors roundup. For annotation-heavy workflows (comments, stamps, drawing tools), we also have a dedicated guide on how to annotate PDFs for free.
Quick Comparison: Best Free PDF Highlighting Tools
| Tool | Platform | Highlight Colors | File Size Limit | Saves Highlights? | Best For |
|---|---|---|---|---|---|
| Adobe Acrobat Reader | Windows, Mac, iOS, Android | 11 colors | No limit | Yes (embedded) | Desktop power users |
| Foxit PDF Reader | Windows, Mac, Linux | 8+ colors | No limit | Yes (embedded) | Linux users, fast rendering |
| Xodo | Web, iOS, Android, Windows | 6 colors | No limit (app), 100 MB (web) | Yes | Cross-platform sync |
| PDF24 | Web | 4 colors | No limit | Yes (flattened) | Quick browser-based work |
| Smallpdf | Web | 5 colors | 5 MB free tier | Yes | Occasional use |
| Sejda | Web, Desktop | 6 colors | 50 MB / 200 pages | Yes | Batch processing |
| PDFescape | Web | 4 colors | 10 MB / 100 pages | Yes | Legacy browser workflows |
| macOS Preview | Mac only | 5 colors | No limit | Yes (embedded) | Mac users who want zero installs |
| Okular | Linux, Windows | 6 colors | No limit | Yes (standalone XML or embedded) | KDE/Linux users |
Method 1: Adobe Acrobat Reader (Desktop – Windows, Mac)
Adobe’s free Reader gets a lot of grief, mostly deserved, but its highlighting is actually solid. You get 11 color options, opacity control, and the highlights embed directly into the PDF so anyone can see them.
How to highlight in Acrobat Reader:
- Open your PDF in Acrobat Reader DC (free download from Adobe).
- Click the highlighter icon in the floating toolbar on the left, or press Ctrl+Shift+H (Cmd+Shift+H on Mac).
- Select the text you want to highlight. It turns yellow by default.
- To change colors: right-click the highlight, pick “Properties,” and choose from the palette.
- Save the file. Highlights are embedded in the PDF itself.
Pros: Embedded annotations (everyone sees them), 11 color choices, keyboard shortcut support, works offline, no file size limits.
Cons: Installer is bloated (500 MB+), tries to upsell you to Acrobat Pro constantly, slow startup on older machines. The free version cannot highlight scanned PDFs – you need OCR first. We cover that in our best free PDF OCR software guide.
Method 2: Foxit PDF Reader (Desktop – Windows, Mac, Linux)
Foxit opens faster than Acrobat. Noticeably faster. If you work with large PDFs (100+ pages), that matters. The highlighting tool works the same way: select text, it gets colored.
Steps:
- Download Foxit PDF Reader (free) from the Foxit website.
- Open your PDF.
- Go to the Comment tab and click Highlight.
- Drag over the text. Default is yellow; right-click the highlight to change color or opacity.
- Save. Annotations embed into the PDF.
Pros: Lightweight (under 150 MB), Linux support (rare for PDF tools), fast rendering, tabbed interface for multiple PDFs. Connected PDF feature lets you track who viewed highlights.
Cons: Asks you to create a Foxit account on install (you can skip it). Some advanced annotation features (like area highlight) require the paid version.
Method 3: macOS Preview (Mac Only)
If you’re on a Mac, you already have a perfectly fine PDF highlighter installed. Preview doesn’t advertise this well, but it handles highlights, underlines, and strikethroughs natively.
- Double-click any PDF – it opens in Preview by default.
- Click the pen icon (Markup Toolbar) or press Cmd+Shift+A.
- Click the highlight button (looks like a marker pen).
- Select text. Done.
- To change colors: click the dropdown arrow next to the highlight button.
Pros: Already installed, fast, no ads, integrates with iCloud. Supports highlight, underline, and strikethrough in the same toolbar.
Cons: Mac only (obviously). Limited to 5 highlight colors. No opacity control. Can occasionally strip highlights when opening files edited in other apps.
Method 4: Xodo (Web + Mobile Apps)
Xodo is what I recommend to people who work across devices. You highlight a contract on your phone during lunch, open the same PDF on your laptop later, and the highlights are there. The web version works without an account for basic highlighting.
- Go to xodo.com or download the app (iOS/Android/Windows).
- Upload or open your PDF.
- Tap the highlight tool in the annotation toolbar.
- Select text. Pick a color from the palette (6 options).
- Download the annotated PDF or save to cloud storage.
Pros: Cross-platform sync, collaborative annotations (share a link and others can highlight too), works offline in the app. The web version handles files up to 100 MB without an account.
Cons: Free tier limits you to 2 documents per day on the web version. The app is unlimited but shows occasional upgrade prompts. Some users report slow rendering on PDFs with heavy graphics.
Method 5: PDF24 (Online – No Install)
PDF24 is a German company that offers a bunch of PDF tools for free, funded by ads. Their online editor includes a highlighter that works directly in your browser. No signup, no file size limit. I’ve pushed 80 MB contracts through it without issues.
- Go to tools.pdf24.org and click “Edit PDF.”
- Upload your file.
- Select the text tool, then switch to the highlighter (marker icon).
- Draw over the text you want highlighted.
- Click “Save” and download.
One thing to know: PDF24 flattens annotations. That means your highlights become part of the page image rather than separate annotation layers. You can’t remove them after downloading. For most people this is fine, but if you need editable highlights, use Acrobat Reader or Foxit instead.
Pros: No account needed, no file size limit, entirely browser-based, GDPR-compliant (files deleted after 1 hour), no watermarks.
Cons: Highlights are flattened (not editable after save), only 4 colors, the interface feels dated. Drawing highlights freehand rather than snapping to text selection means less precision.
Method 6: Smallpdf (Online)
Smallpdf has a cleaner interface than most online PDF tools. The highlighting works well, but the free tier limits you to 2 tasks per day and 5 MB file size. If you just need to highlight one document quickly, that’s enough.
- Go to smallpdf.com and choose “Edit PDF.”
- Upload your file (drag and drop works).
- Click the highlighter tool from the toolbar.
- Select text or draw freehand highlights.
- Download the result.
Pros: Clean UI, fast processing, 5 color options, integrations with Google Drive and Dropbox.
Cons: 2 free tasks per day, 5 MB file size on free tier, Pro costs $9/month. Adds a small “Edited with Smallpdf” metadata tag (not visible in the document, but in file properties).
Method 7: Sejda (Online + Desktop)
Sejda sits between the pure-online tools and full desktop apps. The online version handles files up to 50 MB and 200 pages, which covers most use cases. If you hit those limits, there’s a desktop version too.
- Go to sejda.com and click “Edit PDF.”
- Upload your document.
- Select text and choose “Highlight” from the popup menu, or use the highlight tool from the toolbar.
- Pick a color (6 available).
- Save and download.
Pros: Generous free limits (50 MB, 200 pages), text-selection highlighting (snaps to words), 6 colors, both online and desktop versions available.
Cons: Free tier limited to 3 tasks per hour. The desktop app costs $7.95/week (expensive for what it is). Files are deleted from servers after 2 hours.
Method 8: Okular (Desktop – Linux, Windows)
Okular comes from the KDE project and it’s the best PDF reader on Linux, full stop. Highlighting works well, and you can choose between saving annotations in a separate XML file (Okular-only) or embedding them into the PDF.
- Install Okular from your package manager (Linux) or the Microsoft Store (Windows).
- Open a PDF.
- Press F6 or go to Tools > Review.
- Select the highlight tool.
- Select text in the document. Right-click to change color.
- To embed annotations: File > Save As (not just Save, which keeps them in external XML).
Pros: Open source, free, lightweight, supports PDF/DjVu/EPUB/CBR. Annotation storage options (embedded or external). Active development.
Cons: Default “Save” stores annotations in XML (only Okular can read them) – you must “Save As” to embed. The Windows version through Microsoft Store can be quirky. No mobile apps.
Method 9: PDFescape (Online)
PDFescape has been around since the early 2010s and honestly looks like it. But the highlighting works, it’s free, and it handles files up to 10 MB / 100 pages without an account.
- Go to pdfescape.com.
- Click “Free Online” and upload your PDF.
- Select the “Highlight” tool from the annotation menu on the left.
- Draw over the text areas you want highlighted.
- Click the green “Save & Download” button.
Pros: No account required, works in any browser, completely free for files under 100 pages.
Cons: 10 MB / 100 pages limit, dated interface, freehand highlighting (doesn’t snap to text), only 4 colors, slow with complex PDFs. Flash-era design that never quite got modernized.
How to Highlight Scanned PDFs (No Selectable Text)
Here’s a problem you’ll hit eventually: you try to highlight text in a scanned PDF and nothing selects. That’s because scanned PDFs are basically images wrapped in a PDF container. The document has no actual text layer.
The fix is OCR (Optical Character Recognition). You run the scanned PDF through an OCR tool, which adds a text layer on top of the page images. After that, highlighting works normally.
Free OCR options that work well:
- PDF24 has a free OCR tool at tools.pdf24.org/en/ocr-pdf
- OCRmyPDF (open source, command-line) produces excellent results
- Google Drive – upload the PDF, open with Google Docs, and it runs OCR automatically
For a detailed comparison of OCR tools, see our best free PDF OCR software guide.
Tips for Better PDF Highlighting
Use a color system
Don’t just highlight everything yellow. Set up a system: yellow for key points, green for things you agree with, red for issues or errors, blue for definitions. This makes reviewing highlighted documents much faster, especially in long contracts or academic papers.
Highlight phrases, not paragraphs
I see people highlight entire paragraphs all the time. When you come back to the document later, that giant yellow block tells you nothing. Highlight the specific phrase or sentence that matters. Your future self will thank you.
Check compatibility before sharing
If you’re sending a highlighted PDF to someone else, make sure the highlights are embedded (not stored in external files). Open the PDF in a different app to verify. Okular’s default behavior of saving to XML is the biggest offender here – recipients won’t see your highlights unless you “Save As.”
Flatten before printing
Some printers handle annotation layers poorly. If your highlights look weird when printed, flatten the PDF first. PDF24 and Sejda both have free flatten tools. We covered this in detail in our how to flatten a PDF guide.
Desktop vs. Online Highlighting: Which Should You Use?
Use a desktop app (Acrobat Reader, Foxit, Okular, Preview) if you work with PDFs regularly, deal with large files, or need embedded annotations that survive sharing. Desktop apps also work offline and don’t have file size restrictions.
Use an online tool (PDF24, Smallpdf, Sejda) if you need to highlight something quickly and don’t want to install software. Online tools also work on Chromebooks and locked-down work computers where you can’t install apps. The tradeoff is file size limits and daily task caps on free tiers.
For most people, I’d say start with whatever’s already on your computer. Preview on Mac, Acrobat Reader if you have it on Windows. Only go hunting for alternatives if those don’t work for your specific situation.
FAQ
Is it free to highlight text in a PDF?
Yes. Adobe Acrobat Reader (free version), Foxit Reader, macOS Preview, and Okular all let you highlight PDFs without paying anything. Online tools like PDF24 and Sejda also offer free highlighting with some usage limits.
Can I highlight text in a scanned PDF?
Not directly. Scanned PDFs are images, so there’s no text to select. You need to run OCR (Optical Character Recognition) first to add a text layer. Free OCR options include PDF24, Google Drive, and the open-source OCRmyPDF tool.
How do I highlight a PDF without Adobe?
Foxit Reader (Windows/Mac/Linux), macOS Preview, Okular (Linux/Windows), and browser-based tools like PDF24 or Sejda all support highlighting without any Adobe software. On mobile, Xodo works well on both iOS and Android.
Will my highlights show up when I send the PDF to someone?
It depends on the tool. Adobe Acrobat Reader, Foxit, and Xodo embed highlights directly into the PDF file, so anyone opening the file will see them. Okular saves highlights externally by default (you need to “Save As” to embed them). Online tools generally produce files with embedded highlights.
Can I remove highlights from a PDF after adding them?
Yes, if the highlights are annotation-layer highlights (not flattened). In Acrobat Reader or Foxit, right-click the highlight and select “Delete.” In online tools that flatten highlights (like PDF24), you cannot remove them after saving – the highlights become part of the page image.
What is the best free PDF highlighter for students?
For students, I’d recommend Xodo. It works across phone, tablet, and computer, syncs your annotations, and the mobile app is completely free with no document limits. If you’re on a Mac, Preview is the simplest option with zero setup required.