About annotating PDFs
Annotations are the standard way to review a PDF: marking a contract for a colleague, correcting a draft, or making study notes on a paper. This tool adds them as real PDF annotations, not as part of the page itself. That means anyone who opens the file in Adobe Acrobat Reader, Preview on a Mac, a browser or most other PDF readers sees your highlights and comments, can read them in the comments list, and can reply to, move or delete them. Highlight and underline work on PDFs with real text; on a scanned page there is no text to select, so draw a box or run OCR PDF first. Comments appear as small note icons that open when clicked. The pen is useful for circling, ticking or quick sketches. If you want marks that cannot be removed, such as a stamp, use Edit PDF or Watermark PDF. If you need to hide text for good, use Redact PDF, because a black highlight can be removed.
Limits: one PDF per task, up to 25 MB with a free account, 200 MB on Pro and 500 MB on Business. Browser tools have no daily task limit.
Before you sign in, files can be up to 25 MB. A free account raises this to 25 MB.
Privacy: this tool runs entirely in your browser; the file never leaves your device. Nothing is uploaded, so we have nothing to store or delete.
How to use the PDF tools: Step-by-step help with every tool, limits and your files.
Annotate PDF: frequently asked questions
Will other people see my annotations?
Yes. They are standard PDF annotations, shown in Adobe Acrobat Reader, Preview, browsers and most PDF apps.
Why can't I highlight text on my scan?
A scan is an image with no text layer. Run it through OCR PDF first, then highlight the recognised text.
Can annotations be removed later?
Yes. Anyone with the file can delete or edit them in a PDF reader, which is what makes them suitable for review.
Can I use a black highlight to hide information?
No. The text underneath is still there. Use Redact PDF to remove it permanently.