PDF Highlight Tool
Drag over a rendered page to highlight it, in any colour, and save the marked-up PDF.
Processing: This tool runs entirely in your browser. Your input and any file you open stay on your device — nothing is uploaded to a server.
How to use the pdf highlight tool
- Choose a PDF; the first page is rendered for you.
- Drag across anything you want to highlight, changing colour as needed.
- Move through the pages, then save the marked-up file.
About this tool
The page is rendered, you drag over what matters, and the marks are written into the file. Colour and opacity are adjustable, marks accumulate across pages, and the last one can be undone.
What this writes are semi-transparent rectangles drawn onto the page, not PDF annotation objects. The difference is practical rather than pedantic: a real annotation can be selected, edited, replied to and deleted in a reader, while a drawn rectangle is part of the page. That suits sending someone a marked-up copy and does not suit a document that will be annotated further by a team. Saying which one you are getting is more useful than implying they are the same.
A rectangle drawn on screen has to cross two conversions before it lands: the render scale, and PDF's y axis, which runs upward from the bottom-left while the screen's runs down from the top-left. Getting one without the other places the highlight on the mirror image of the line you marked — so the conversion is a tested function rather than something checked by eye.
A click that is not a drag is ignored, because a stray zero-width rectangle in a document is invisible until someone opens it in an editor.
Common uses
- Marking the clauses that matter before sending a contract on.
- Highlighting findings in a report for a colleague.
- Picking out figures in a statement or an invoice.
Frequently asked questions
- Can the highlights be removed later?
- Not in a reader. They are drawn onto the page rather than added as annotation objects, so they behave like part of the document. Keep the original if you may need a clean copy.
- Why not use real PDF annotations?
- They would be editable and repliable, which is better for collaboration — and considerably more machinery. This is the version that works today, and the page says which one you are getting.
- Does the highlight cover the text?
- No. It is drawn semi-transparently over the page, so the text stays readable underneath, which is what the opacity control adjusts.
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