Highlight PDF

What does the Highlight PDF tool do?

The FreePDF Highlight tool opens your PDF in the browser editor with highlight colours ready to use. Mark important passages in yellow, green, blue, pink, purple or orange — just like a real marker.

Highlights are added as a transparent overlay, so the text underneath stays perfectly readable, and they are baked into the PDF on export.

How to highlight

1. 1
   Open your PDF in the editor

   Drag and drop the document you want to highlight.

2. 2
   Pick the Highlight tool

   Choose a marker colour from the properties panel.

3. 3
   Mark the passages

   Swipe or click-drag across the text you want highlighted, page by page.

4. 4
   Download the result

   Highlights are written into the document with pdf-lib in your browser.

What FreePDF Highlight PDF can do

• Eight marker colours
• Transparent overlay keeps text readable
• Works on scanned documents too
• Works entirely in your browser

Privacy — your files stay on your device

Highlight PDF runs entirely inside your browser using the same open-source engine stack that powers all FreePDF tools. Your files are loaded into browser memory, processed on your CPU, and written back out as a direct download. Nothing is sent to any server — you can verify this in your browser devtools → Network tab. Close the tab and everything is cleared from memory.

Supported devices and browsers

Known limitations

FreePDF is honest about what it can and cannot do:

• Highlights are page overlays — they don't bind to the underlying text stream
• Very fine highlighting precision depends on zoom level
• Not searchable like real PDF highlight annotations