PDkef
Highlight PDF
On-device

Highlight PDF Online Free: Add Comments to Any Page

Open a paper and drag along a line to highlight it, the way you would with a marker. Rest on a highlight to change its color or add a comment beside it. Free, open source, and your file stays on your device.

Select or drop a PDF to highlightLet go to add your file

Private. Files never leave your device.

Open a different file?

This closes the current PDF. It stays in your recent files with everything you've done, so you can come back to it from the home page.

Clear all files?

This empties the list and the order you put it in. Nothing is removed from your device.

Turn on airplane mode and give it a try. It still works.

How it works

How it works

How to highlight text in a PDF

A PDF highlighter should feel like the marker on your desk. Open the PDF and drag along the lines you want to keep: the highlight stays straight along the line, works on scanned pages too, and everything runs in your browser.

  1. 1Open your PDF. Drop in a paper, a chapter or a scanned page, on a computer or an iPad. A yellow marker is already in your hand.
  2. 2Drag along a line. The highlight follows the line and stops at the end of its column. Double-click marks a word, and a third click its sentence.
  3. 3Change it or add a comment. Rest on a highlight for its colors, underline and Comment. Then download, and your marks open in any PDF viewer.

Free for everyone

Highlight as many pages as you like, with no account and no watermark. Highlights and comments are saved as standard PDF annotations, so they open in other PDF viewers too.

It's open source under the MIT license, so anyone can read the code, fork it on GitHub, or share it. Simple PDF tools should be free for everyone.

Got questions?

Frequently asked questions

Is Highlight PDF free?

Yes. Like every tool on PDkef, it is free with no signup, no watermark and no page limit.

Is my PDF uploaded?

No. The highlighting, the comments and the download are all made in your browser. Your file never leaves your device, and there is no processing server.

How do I highlight text in a PDF?

Open the PDF and drag along the line you want, as you would with a marker. Drag down to carry the highlight onto the next lines. Double-click marks one word and a third click its whole sentence.

How do I change or remove a highlight?

Rest the pointer on it, or tap it on a touch screen. Its toolbar offers six colors, underline, Comment and Delete. Whatever you pick becomes your marker for the next lines.

Can I highlight a scanned PDF?

Yes. The highlight reads the lines from the page image itself, so a scanned page or a photo of a book page works too, with no text layer needed.

Does it work on a Mac and an iPad?

Yes. It runs in Safari and Chrome on a Mac and in Safari on an iPad. On a touch screen, tap a highlight to open its toolbar.

Will my comments show in other PDF viewers?

Yes. Highlights and comments are saved as standard PDF annotations, so they show in any PDF viewer, and they come back editable when you open the file here again.

Can I annotate a PDF here?

Yes, the way you annotate when you read: highlight or underline the lines that matter and add a comment to any highlight. They are saved as standard PDF annotations. For text boxes, shapes or a signature, use Sign & Fill PDF.

Can I highlight Hebrew or Arabic text?

Yes. On a right-to-left page the highlight follows the line from right to left, and a clicked word or sentence fills in from its first letter.

Same suite

More PDF tools

Every one of these runs on your device, free, with nothing uploaded.

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