pdfcosmos

Highlight PDF

Drag a highlighter over any PDF and download the result, entirely in your browser.

Free, fast, and privacy-first.

Add the PDF you want to highlight

or drag & drop a file here

PDF onlyone fileup to 100 MB

Highlight a PDF — mark text in any color, like a real highlighter

Highlighting a PDF here works just like a highlighter pen: drag a band over the text you want to mark, then fine-tune its size, color, and opacity. Each highlight is drawn with a “multiply” blend, so the color sits over the page while the darker text shows straight through and stays perfectly readable — no washed-out or hidden words. Because the band is placed freely on the page, it works on any PDF, including a scanned or printed document that has no selectable text layer.

Pick any color — classic yellow for study notes, or a set of colors to code a contract or a research paper — and mark as many passages as you like before downloading. The highlights are drawn straight onto the page in your browser with pdf.js and pdf-lib, so your file is never uploaded and never leaves your device. To add your own text, checkmarks, or a signature as well, use Fill & Sign; to stamp one mark across every page, use Add Watermark.

  • Text stays readable

    A multiply blend keeps your words sharp under the color, exactly like a real highlighter.

  • Any color, any opacity

    Mark in yellow or colour-code with several shades, and adjust how strong each band is.

  • Works on scanned PDFs

    Highlights are placed freely, so they work even on a page with no text layer.

  • Nothing is uploaded

    Highlighting happens in your browser with pdf-lib. Your file never leaves your device.

How to highlight a PDF

  1. Add your PDF

    Click “Select PDF”, or drag a single file into the upload area. Any PDF works, even a flat scan.

  2. Add a highlight

    Click “Highlight”, then click the text you want to mark. Drag or resize the band to fit the line, and pick any color and opacity.

  3. Download

    Download your highlighted PDF. The highlight is drawn straight onto the page.

Frequently asked questions

Are my PDF files uploaded to a server?
No. Your PDF is rendered and highlighted entirely in your browser with pdf.js and pdf-lib. The file never leaves your device. You can confirm it in your browser's Network tab: no file data is sent.
Will the highlight cover up my text?
No. Each highlight is drawn with a “multiply” blend, exactly like a real highlighter pen. The color sits over the paper but the darker text shows straight through, so it stays readable.
Can I highlight a scanned PDF?
Yes. The highlight is placed freely on the page, so it works on any PDF, including a scanned or printed page that has no text layer. Just drag the band over the area you want to mark.
Can I remove the highlight later?
The highlight is burned onto the page, so it isn't a separate annotation you can click to delete afterwards. Keep your original file if you may need an unmarked copy, and highlight a duplicate.
Can I also add text, a checkmark, or a signature?
Yes. Use our Fill & Sign PDF tool to place your own text, checkmarks, dates, a drawing, or a signature anywhere on the page. To stamp one mark across every page, see Add Watermark.
Is Highlight PDF free?
Yes, it's completely free to use, with no sign-up and nothing to install.