How to highlight and mark up a PDF
Updated October 25, 2026
Highlight important passages, draw arrows and notes, and mark up a PDF for review, right on the page.
Mark up instead of printing
Reviewing a contract, studying a paper or checking a proof is easier with a highlighter in hand. PDF One gives you the same thing on screen: fluorescent highlighters, a brush for underlines, circles and handwritten notes, and an eraser.
Step by step
- Open the PDF in PDF One and choose Paint, Highlight & Eraser.
- Pick the highlighter and one of the fluorescent colours (yellow, green, pink, blue, orange or purple).
- Drag across the text you want to highlight. Straight strokes snap neatly along the line.
- Switch to the brush to underline, circle or write a short note. Change brush size and opacity as needed.
- Use the eraser to remove a stroke, or Clear Page Paint to start the page over.
- Click Done Painting, then Save a copy.
Colour coding that works
A simple system helps when you come back to a document later: for example, yellow for key facts, green for things you agree with, pink for questions or problems. Keep the number of colours small so the page stays readable.
Covering content is not the same as removing it
Painting a black box over text hides it visually, but you should always check the saved file before sharing it, and for sensitive material the safest choice is to remove the whole page (see how to split a PDF) or to save the page as an image. Never rely on a cover-up you have not checked.