How to Edit and Annotate a PDF Online for Free

What 'editing' a PDF actually means

PDFs are a fixed-layout format: pages are rendered, then locked. You can't easily change the words a PDF contains the way you would a Word document. What you can do is mark it up — add text, draw, highlight, and box important areas — and save that as a new file.

That covers the vast majority of real use: signing approvals, annotating feedback on a design, marking up a scan of a contract, or highlighting key passages to send to a colleague.

Annotating without uploading your file

The PDF Editor runs entirely in your browser. It renders your document with the pdf.js engine and stores every annotation you add as resolution-independent page coordinates, so your marks stay crisp no matter how much you zoom.

Choose a tool from the toolbar — text, pen, box, highlight, or arrow — pick a color, stroke width, and font size, then click or drag on the page. Because nothing is uploaded, the tool stays fast and is safe to use with confidential documents.

Marks you place aren't permanent. Switch to the Select tool to click any annotation and edit, move, or resize it: text reopens for changes, drag moves it, and rect/highlight handles resize it. Keyboard shortcuts keep editing fast — Ctrl/Cmd+Z and Ctrl/Cmd+Shift+Z for undo/redo, and the Delete key to remove the selected mark.

Saving your edited PDF

When you're done, hit Save PDF. The editor flattens every annotation onto the page at a high export resolution and embeds it into a fresh PDF matched to your original page size.

The result is a normal, shareable PDF that opens in any viewer — the text, highlights, and drawings are baked in as part of the page, not separate attachments that can mis-sync.

Undo, redo and precision

Mistakes happen. The editor keeps a full undo/redo history per page, and the select tool lets you click any annotation and delete it, so you can refine a mark-up until it's exactly right before saving.

You can also control font size for text and stroke width for drawing — the two controls people reach for most when polishing an annotation.