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Annotate & Highlight PDFs

Highlight (5 colors), add notes and freehand drawings to PDFs — saved as native /Highlight objects per ISO 32000-2. Free, no upload, runs in browser.

  • Highlight text, add sticky notes, and draw freely
  • Annotations saved locally in your browser
  • Export to PDF with annotations embedded

Annotating a PDF lets you add highlights (5 colors), sticky notes and freehand drawing — saved as native PDF /Highlight annotation objects per ISO 32000-2 §12.5.6.10. OpenPDF supports all 3 markup types and exports a standard PDF that Adobe Reader, Preview and every other PDF editor can read, edit and remove later. Nothing is flattened into pixels unless you choose to, so contracts and design reviews stay editable downstream.

How it works

  1. Open your PDF. Drop a PDF onto OpenPDF to load it into the annotation view.
  2. Pick an annotation tool. Choose highlight, sticky note, or freehand drawing from the toolbar.
  3. Mark up the document. Click or drag to apply annotations. Everything stays locally — nothing is sent to a server.
  4. Export with annotations. Download the annotated PDF with all marks embedded as proper PDF annotations.

Common use cases

  • Marking up a contract with highlights and sticky notes during a remote review call.
  • Adding feedback to a design PDF without exporting to a dedicated markup tool.
  • Circling corrections on a scanned document and sending the annotated copy back.
  • Attaching comments to a lease before sending it to a co-tenant for review.

Frequently asked questions

Are annotations embedded as proper PDF annotations?

Yes. OpenPDF exports annotations using pdf-lib so they appear as standard PDF annotations in Adobe Reader, Preview and other PDF viewers — not as flattened pixels.

Can I remove annotations later?

Annotations are saved as overlay objects inside the PDF. Any PDF editor that understands annotation objects (Adobe Reader, Preview, most online editors) can edit or remove them.

Are my annotations autosaved?

The in-browser state is saved locally while you work. The final export happens when you click Download — at that point the annotated PDF is produced and written to your device.

Is anything uploaded?

No. Annotations are composited with pdf-lib locally in your browser.

Why OpenPDF

OpenPDF is an independent project built around one principle: the PDFs you edit should never leave your device. Every tool — merge, split, sign, organize, annotate, compress, watermark, add page numbers — runs entirely in your browser using WebAssembly and modern JavaScript APIs. There is no upload step, no account, no email harvesting, and no premium tier gating the useful features. The codebase and the third-party scripts loaded for analytics and advertising are visible in the page source — Google AdSense and Google Analytics 4 load only after you accept cookies in the consent banner — so anyone can audit what is running before trusting the tool with sensitive contracts, scanned IDs, or financial documents.

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