Highlighting a PDF should be simple. And it is — once you know where to look. Whether you are studying, reviewing a contract, or marking up a report, here is every free way to highlight PDFs on any device.

Highlight PDFs on Mac (Using Preview)

The fastest method if you own a Mac:

1. Open your PDF in Preview
2. Select the text you want to highlight
3. Go to Tools > Annotate > Highlight Text
4. Or just right-click the selected text and choose Highlight
5. Change the highlight color by clicking the down arrow next to the highlight button

Preview gives you yellow, green, blue, pink, and purple highlight colors. It also supports underline and strikethrough.

Highlight PDFs on Windows

Microsoft Edge (Built-in)

1. Open the PDF in Microsoft Edge
2. Select the text you want to highlight
3. Right-click and choose Highlight
4. Pick your color from the options
5. Save the file

Using Adobe Acrobat Reader (Free)

1. Download Adobe Acrobat Reader DC (free version)
2. Open your PDF
3. Click the Highlight tool in the toolbar
4. Drag across the text you want to highlight
5. Save your changes

Acrobat Reader gives you the most control over highlight colors and opacity. The free version includes all basic annotation tools.

Highlight PDFs on iPhone

1. Open the PDF in the Files app
2. Tap the Markup button (pen icon)
3. Tap the + button and select Highlight
4. Drag to select the text area
5. Choose a color from the palette
6. Tap Done to save

Apple Books also supports highlighting if you prefer reading PDFs there.

Highlight PDFs on Android

1. Open the PDF in Google PDF Viewer or Google Drive
2. Tap the Edit icon
3. Select the Highlight tool
4. Drag over the text you want highlighted
5. Save the file

Free Online PDF Highlighters

No downloads needed for these:

• PDFescape — Free online editor with highlight tool, no account needed for basic use
• Sejda — Clean, fast, and supports multiple highlight colors
• Xodo PDF Studio — Browser-based with full annotation tools

For sensitive documents, use offline tools instead of uploading to websites.

Highlight Tips That Save Time

• Use different colors for categories — Yellow for key facts, green for quotes, pink for things to research further
• Add notes to highlights — Most tools let you attach a comment to any highlight, which is invaluable for studying
• Export highlighted text — Some readers like Acrobat can extract all highlighted text into a summary document
• Keyboard shortcuts — On Mac Preview, use Cmd+Ctrl+H to highlight selected text instantly

Common Issues and Fixes

• Cannot highlight scanned PDFs — Scanned PDFs are images, not text. You need to run OCR first to make text selectable. Check out our guide on making scanned PDFs searchable.
• Highlights not saving — Make sure you are editing a local copy, not a read-only file. Save with a new filename to be safe.
• Wrong color selected — Most tools remember your last color. Right-click the highlight to change it after the fact.