Annotate PDF Online Free — Add Notes & Comments

Why annotate a PDF?

Adding notes directly to a PDF is often faster than editing the original document. Highlighting important text, leaving feedback, marking corrections, or adding approval comments can all happen right inside the file, without touching the underlying content.

PDFly annotates entirely in your browser, so the document stays on your device the whole time — no sign-up, no software, no watermark on the finished file. Works on desktop and mobile browsers alike.

Common uses

Review contracts
Highlight important passages
Leave document feedback
Mark proofreading corrections
Add approval notes
Comment on shared PDFs

Best Practices & Limitations

Tips for best results

Use different colors consistently — e.g. yellow for questions, red for corrections — so reviewers can scan annotations quickly.
Keep comments short; long notes are easier to read as a separate summary page or email.
Flatten the PDF afterward with Flatten PDF if you need to guarantee annotations can't be moved or deleted by the next person.

Limitations & when not to use this tool

Annotations follow the standard PDF comment format — some older readers may display them differently or not at all.
Not built for full-page mark-up/redlining workflows with track-changes style comparison; use Compare PDF for that.
Very dense annotation (dozens of overlapping notes) can get visually cluttered on smaller screens.

About annotate PDF

Add notes, comments, and visual annotations to PDF pages for review and collaboration. Annotation keeps feedback attached to the document instead of requiring a separate message thread.

Common uses for annotate PDF

Useful for students, reviewers, editors, teams, contracts, drafts, and documents that need comments before final approval.

Tips for using this PDF tool

Keep annotations concise and check how they appear when the PDF is opened in another viewer.

Related PDF tools

Want a step-by-step walkthrough? Read the Annotate PDF guide.

Frequently asked questions

Can I highlight text in scanned PDFs?

Scanned PDFs are image-based, so selectable text may not be available. You can still place annotations on the page, but text-specific highlighting depends on the PDF having selectable text.

Will my existing formatting change?

No. Annotations are added on top of the original PDF without changing its layout, fonts, or page order.

Can I edit or remove annotations later?

Yes, as long as you're still working in the editor before downloading. After saving, further edits depend on whether the PDF software you open it in supports editing existing annotations.

Does this work with password-protected PDFs?

Some password-protected or DRM-restricted PDFs can't be modified. If editing permissions are disabled, you'll need an unrestricted copy before adding annotations.

Common workflow

PDF EditorAnnotate PDFSign PDF