PDF Highlighter Tool: How to Highlight Text in PDFs Online for Free

Highlighting text in a PDF is one of the most common things people need to do with documents. Whether you are studying, reviewing a contract, or collaborating on a report, a good PDF highlighter saves time and keeps your annotations organized. This guide covers the best free tools and methods for highlighting PDFs in 2026.

Why Use a PDF Highlighter?

Digital highlighting beats physical highlighting in several ways:

• Non-destructive: You can remove highlights without damaging the document
• Color-coded: Use different colors for different categories (important, question, follow-up)
• Searchable: Many tools let you search within your highlights
• Shareable: Collaborators can see your highlights and add their own
• Exportable: Extract highlighted text into summaries or notes

Best Free Online PDF Highlighters

1. PDFescape

PDFescape is a browser-based PDF editor with a solid highlighting feature. Open your PDF in the online editor, select the highlight tool, choose your color, and drag across text. It supports multiple highlight colors and lets you add comments attached to each highlight. The free tier works for PDFs up to 100 pages and 10 MB.

2. DocFly

DocFly offers a clean online PDF editor with highlighting and annotation tools. Upload your PDF, use the highlight tool from the toolbar, and drag to select text. You can change highlight colors and opacity. The free tier allows three documents per month with full annotation features.

3. Sejda

Sejda provides a no-frills PDF editor that includes text highlighting. It is fast, does not require an account for basic use, and processes files without storing them long-term. Upload, highlight, download. The free tier handles files up to 200 pages or 50 MB.

Best Free Desktop PDF Highlighters

4. Xodo PDF Studio

Xodo offers one of the smoothest PDF annotation experiences. Available as a web app, Windows app, and mobile app, Xodo lets you highlight with multiple colors, add sticky notes, draw shapes, and underline text. All annotations are standard PDF annotations, meaning they show up in any PDF reader. The basic highlighting features are free.

5. Foxit Reader

Foxit Reader is a free PDF reader with built-in annotation tools, including highlighting, underlining, strikethrough, and comment notes. It is lighter and faster than Adobe Reader for most tasks. The highlight tool supports custom colors and you can export a summary of all your annotations.

6. Adobe Acrobat Reader

The free version of Adobe Acrobat Reader includes a highlight tool. Select text, right-click, and choose Highlight. You can also use the Comment toolbar to access highlighting, sticky notes, and drawing tools. It is the most widely used PDF reader, so your highlights will display correctly for anyone else who opens the file.

Highlighting PDFs on Mobile

iPhone and iPad

• Apple Books: Open PDFs in Apple Books and use the built-in highlight tool. Tap and hold text, then select Highlight.
• Files app: iOS supports basic PDF markup. Open a PDF in Files, tap the markup button, and use the highlight tool.
• Xodo (iOS app): Full-featured PDF annotation with highlighting, notes, and drawing.

Android

• Google PDF Viewer: Basic highlighting built into Android's default PDF handler
• Xodo (Android app): The best free PDF annotator on Android, with cloud sync
• Adobe Reader (Android): Highlighting and commenting features available for free

How to Highlight Efficiently

• Use color coding: Yellow for important facts, green for definitions, pink for questions, blue for action items
• Don't over-highlight: If everything is highlighted, nothing stands out. Highlight only key phrases, not full sentences.
• Add comments: Attach a note to highlights explaining why you marked them. Future you will thank you.
• Export summaries: Many tools can generate a summary page listing all highlighted text. Use this for study notes or meeting prep.

Highlighting Scanned PDFs

Scanned PDFs are images, not text. Standard highlighting tools will not work because there is no text layer to select. You have two options:

1. Use OCR first: Run the scanned PDF through an OCR tool to add a text layer, then highlight normally.
2. Use a rectangle tool: Most PDF editors let you draw a semi-transparent colored rectangle over the area you want to "highlight." This looks like a highlight but works on images.