This tool adds real annotations to a PDF, freehand pen strokes, a semi-transparent highlighter, shapes (rectangles, circles, lines, arrows), sticky notes, and a text-highlighter that snaps to actual lines of text rather than just drawing a rough box over them. It's built for marking up a draft, highlighting key clauses in a contract, or sketching a quick diagram directly on a page.
The text-highlight tool specifically uses the PDF's real text positions (via pdf.js) to find and highlight whole lines accurately, rather than eyeballing a semi-transparent rectangle. Every annotation supports undo/redo, layering (bring to front / send to back), and full touch support, including pinch-to-resize, you can annotate comfortably on a phone, not just a desktop with a mouse.
On export, everything is flattened permanently into the PDF, so your annotations become part of the document rather than a separate, removable layer. As with the rest of the editing tools, all of this runs in your browser: the page renders via pdf.js, your annotations live on an interactive canvas, and pdf-lib bakes them into the final file, nothing about your document is ever uploaded.
This gets used for the everyday work of reviewing something on paper's digital equivalent, circling a figure that looks off in a report, highlighting the clause a client should look at in a contract, sketching an arrow between two points on a diagram, or leaving a sticky note with a quick comment for a collaborator. Because every tool works with touch, it holds up well for marking up a document on a tablet during a meeting, not just at a desktop with a mouse.
Layering support means a sticky note or shape can sit cleanly above or below other annotations, so a busy, heavily marked-up page still stays readable and organized rather than becoming a jumble.
How to Annotate & Highlight
- Upload your PDF.
- Pick a tool from the toolbar, pen, highlighter, shape, sticky note, or text-highlight.
- Draw directly on the page; switch to Select to move, resize, or delete anything you've added.
- Save to flatten your annotations permanently into the PDF and download it.
Frequently asked questions
Can I highlight actual text, not just draw a box over it?
Yes. The text-highlight tool uses the PDF's real text positions to snap to whole lines, so it lines up accurately instead of approximating with a rectangle.
Can I undo a mistake?
Yes, undo and redo are supported for every annotation you make, up to the last several actions.
Will my annotations be removable after I download the file?
No. Annotations are flattened into the page's actual content on export, so they become a permanent part of the PDF.
Does drawing work on a touchscreen?
Yes, the whole canvas is built on native touch/pointer events, including pinch gestures, so it works naturally on phones and tablets.
Is my document uploaded while I'm annotating it?
No, annotation happens entirely in your browser, nothing is sent to a server at any point.
Related tools
- Add Text & Images: Place text boxes and images anywhere on a PDF page.
- Add Watermark: Stamp a text or image watermark across every page.
- eSign PDF: Draw your signature and place it anywhere on a page.
- Redact PDF: Permanently black out sensitive text or areas.