How to Highlight Text in PDF Online Free

Highlighting text in a PDF is one of the most common annotation tasks. Whether you are studying, reviewing a contract, or marking up a report, being able to highlight PDF text helps you focus on what matters. This guide covers every way to highlight text in PDF files for free in 2026, from browser-based tools to desktop software and mobile apps.

Why Highlight Text in PDFs

PDF highlighting serves many purposes across different workflows:

Studying and research: Mark key passages in academic papers, textbooks, and study materials
Legal review: Flag important clauses, obligations, and deadlines in contracts
Collaborative editing: Draw attention to sections that need revision or discussion
Personal reference: Highlight sections of manuals, guides, and documentation for quick access later
Compliance review: Mark regulatory requirements and action items in policy documents

Method 1: Highlight PDF Text Online (Fastest)

Online tools are the fastest way to highlight PDF text when you do not want to install software.

Using PeacefulPDF to Highlight Text

PeacefulPDF offers a free, browser-based PDF highlighter:

Open the PeacefulPDF annotation tool in your browser
Upload your PDF file
Select the highlight tool from the annotation toolbar
Choose your highlight color (yellow, green, blue, pink, or orange)
Click and drag over the text you want to highlight
Download your annotated PDF when finished

The tool supports multiple highlight colors so you can color-code your annotations. Your file is processed securely and not stored after you download it.

Other Free Online PDF Highlighters

Several other tools let you highlight PDF text in your browser:

Sejda PDF Editor: Free online editor with a highlight annotation tool. Upload your PDF, select text, and apply highlights. Free for documents up to 200 pages or 50 MB.
PDF24 Tools: Completely free annotation tool with highlighting and other markup features. No daily limits.
DocFly: Browser-based PDF editor with highlighting. Free tier allows basic annotation on limited documents.
PDFescape Online: Free online PDF editor with highlight, comment, and drawing tools. Works entirely in your browser.

Method 2: Highlight PDF Text on Desktop

Desktop software offers more powerful annotation features and works offline.

Highlight with Adobe Acrobat Reader (Free)

Adobe Acrobat Reader DC is free and includes a highlight tool:

Download and install Adobe Acrobat Reader from the official website
Open your PDF file in Acrobat Reader
Select the Highlight Text tool from the comment toolbar at the top
Click and drag over the text you want to highlight
Right-click the highlight to change its color, add a comment, or adjust opacity
Save the file to keep your highlights

Adobe Acrobat Reader also lets you add sticky notes to highlights, making it a solid choice for collaborative review workflows.

Highlight with Preview (Mac)

Mac users can highlight PDFs without installing additional software:

Open the PDF in Preview
Click the Markup Toolbar button (pen icon) to show annotation tools
Select the Highlight tool from the toolbar
Choose a color from the highlight color options
Click and drag over the text you want to highlight
Save the document to keep your annotations

Preview supports multiple highlight colors and lets you add notes to each highlight.

Highlight with Xodo PDF Studio (Cross-Platform)

Xodo offers a free PDF reader with annotation features for Windows, Mac, and Linux:

Download Xodo PDF Studio from the official website
Open your PDF file in Xodo
Click the Highlight tool in the annotation toolbar
Select your preferred color and opacity
Drag across the text to apply the highlight
Save the annotated file

Method 3: Highlight PDF Text on Mobile

Highlighting on mobile is useful when you are reviewing documents on the go.

iOS (iPhone and iPad)

Files app (iPadOS): Open a PDF in Files, tap the markup icon, and use the highlight tool on your text
Adobe Acrobat Reader: Free app with full highlighting features. Tap the comment icon, select highlight, and drag over text
PDF Expert: Powerful PDF annotation app with customizable highlight colors and styles. Free tier includes basic highlighting
Apple Books: If your PDF is in your Books library, you can highlight text directly in the reading view

Android

Adobe Acrobat Reader: Same highlighting features as the iOS version. Select text and choose highlight from the popup menu
Xodo PDF Reader: Free app with excellent highlighting and annotation tools
Google PDF Viewer: Basic highlighting support for quick annotations
MuPDF: Lightweight, free PDF viewer with highlighting capability

Tips for Effective PDF Highlighting

Make the most of your PDF highlights with these practical tips:

Use color coding: Assign different colors to different types of information. For example, yellow for important facts, green for action items, and pink for questions.
Add comments to highlights: Most tools let you attach notes to highlighted text. This adds context and makes your annotations more useful later.
Highlight sparingly: If you highlight everything, nothing stands out. Be selective and focus on truly important passages.
Use strikethrough for deletions: Instead of just highlighting text you want to remove, use the strikethrough tool to clearly mark deletions.
Export your highlights: Some tools let you extract highlighted text into a summary document. This is valuable for research and study notes.

Can You Highlight Text in Scanned PDFs?

Highlighting text in a scanned PDF requires an extra step. Scanned PDFs are essentially images, so the text is not selectable or highlightable until OCR (Optical Character Recognition) is applied.

Here is how to handle this:

Run the scanned PDF through an OCR tool first to make the text selectable
Once OCR is applied, use any standard highlight tool to mark the text
Some tools like Adobe Acrobat Pro apply OCR automatically when you try to highlight
Free OCR options include Google Drive (uploads and converts), OCR.space (online), and Tesseract (command line)

If OCR is not available, you can still add visual highlights using a rectangle or drawing tool over the scanned text area, though this is less precise than true text highlighting.

Common Highlighting Issues and Solutions

Cannot select text to highlight: The PDF may be a scanned image. Apply OCR first to make text selectable.
Highlights do not save: Some PDF viewers only save highlights in a session. Make sure you are saving the actual PDF file, not just the view state.
Highlight tool is grayed out: The PDF may have security restrictions that prevent annotations. Check if the file has editing restrictions enabled.
Highlights appear in wrong position: This can happen with non-standard PDF layouts. Try a different annotation tool.
Too many highlights clutter the page: Use the comment pane to manage and navigate your highlights without cluttering the document view.

Highlighting for Different Use Cases

Academic Study

When highlighting for study purposes, create a consistent color system. Highlight main ideas in one color, supporting evidence in another, and terms or definitions in a third. Add margin notes summarizing highlighted sections for quick review.

Contract Review

For legal documents, highlight obligations, deadlines, and key terms. Use one color for things you must do and another for things the other party must do. Flag any clauses you want to negotiate with a different color.

Collaborative Editing

When multiple people review the same document, each person should use a unique highlight color. This makes it easy to see who marked what. Most professional annotation tools support this workflow.

Which Method Should You Use?

Quick annotation: Use an online tool like PeacefulPDF. No installation, works immediately.
Frequent highlighting: Install Adobe Acrobat Reader (free) or use Preview on Mac. Full-featured and works offline.
Mobile annotation: Use Adobe Acrobat Reader or PDF Expert on iOS, Xodo on Android.
Collaborative review: Use a tool that supports comments and shared annotations like Adobe Acrobat Reader.
Academic study: Choose a tool that lets you export highlighted text as notes or summaries.

Highlighting text in PDFs is a straightforward process once you have the right tool. Whether you need a quick online highlighter or a full desktop annotation suite, free options are available for every platform. Pick the method that matches your workflow and start marking up your documents.