How to annotate and highlight a PDF with OnyxPDF
- Drop your PDF into the tool and pick a page.
- Choose a tool: highlighter, freehand pen or note label — and a colour.
- Drag highlights and strokes over the content; type labels where needed.
- Move through the pages, then click “Save” to bake the markup in.
Why do it in your browser instead of uploading?
- No upload: review a confidential draft on your own device.
- Free — Smallpdf keeps annotation in Pro; here highlights, drawing and labels cost nothing.
- Markup is baked into a standard PDF, so recipients see it in any reader without special software.
- Overlay method preserves the original text underneath — highlights stay translucent.
Good to know (honest limits)
- Annotations are baked in on save — they become part of the page, not removable comment objects. Keep the original if you need a clean copy.
- No threaded comment discussions or @mentions: this is markup, not a collaboration platform (those need servers and accounts).
Frequently asked questions
Can recipients remove my highlights?
The markup is flattened into the saved PDF, so it is part of the document rather than a removable annotation layer. Share the original separately if a clean copy is needed.
Can I highlight text precisely?
Drag a translucent rectangle over the passage — it snaps to where you draw it and the text shows through.
Does it work for studying?
Yes — highlight lecture PDFs, mark up readings and add margin notes, all without an account.
Is my document uploaded?
No. Pages render locally and the annotated PDF is assembled in your browser.