How to Highlight Text in a PDF (Free)

Highlighting text in a PDF works like a marker on paper: you colour over the words that matter so they stand out on a skim. How to highlight text in a PDF is, for an electronic document, a matter of selecting a text block and applying a semi-transparent marker colour — and knowing that a highlight is an overlay on the page, which decides whether it prints. Both the how and the caveats are covered here.

How to highlight text in a PDF

Open the Edit PDF tool, click the line of text you want to mark so it registers as a block, and tap a highlight colour from the toolbar. The marker appears behind the text instantly, you can change or clear it at any time, and the finished file saves with the highlights baked into the page.

1. 1Open the Edit PDF tool and add your PDF.
2. 2Click the text to highlight — a block toolbar appears.
3. 3Choose a highlight colour from the swatches.
4. 4Repeat for every section you want to mark; use the minus button to remove a highlight.
5. 5Save and download the highlighted PDF.

Build a colour system for real reviews

• Yellow for "check this" and points that need a decision
• Green for approved or confirmed content
• Red or pink for action items and things that must change
• Blue for definitions, terms and references you will return to
• One colour per issue type, and a short legend if someone else reviews the file after you

Does a highlight print and survive when I send the PDF?

Highlights written into the page render in other readers and are part of the downloaded file — but whether they appear on a printout depends on the reader's settings, since some printers skip page overlays by default. When a highlighted copy must come out exactly as seen, flatten it before printing or sending, and others can no longer move or delete the marks either. The full behaviour of overlays is the annotation question, covered in the related post.

When you cannot highlight — scanned pages

A scanned or photographed PDF has no text objects, only pixels, so there is nothing to attach a marker to. The honest route is OCR, which creates a text layer and makes the page searchable and copyable — but OCR does not erect highlightable text-block objects either. If a scan genuinely needs marking, the practical answers are printing and hand-marking, or editing the original document and re-exporting.

Highlight while you read, not after

The highest-value use of a highlighter is during the reading itself: mark a clause when it matters, not when you page back. Work in short passes — highlight and move on — then use a clear pass before sending so an accidental mark does not travel with the document. A highlight left where it does not belong reads as carelessness on a document that is going to a client or an authority.