About

PDF Annotate

Add highlights, freehand markup, text boxes, and shapes to a PDF in your browser. Nothing is uploaded — all changes are stamped onto the file locally and you download the result.

Drop a PDF here or
  1. Drop a PDF onto the page or browse for one.
  2. Pick a tool from the toolbar — Pen for freehand, Highlighter for semi-transparent strokes, Text for typed notes, Rectangle for boxed callouts.
  3. Draw on the rendered page. Use the Previous / Next buttons to move between pages.
  4. Click "Download annotated PDF" — your annotations are stamped into a new PDF file you can save locally.
What does it do?

A client-side PDF annotator. The PDF is rendered into a canvas with pdf.js, and your strokes / highlights / text / shapes are kept as overlay objects until you save. On save, every annotation is drawn into the PDF using pdf-lib so the result is a single self-contained file — no extra annotation layer that other readers might hide. Everything happens in your browser tab; the file never leaves your device.

Example

Drop a contract, switch to Highlighter, drag across the clause you want to flag, switch to Text, click in the margin, type "review with legal," then click Download. The downloaded PDF opens in any reader with the highlight and the margin note baked in — no special viewer needed.

Common errors and pitfalls

A few cases where the tool can't help — most are inherent to the PDF format rather than the editor.

  • Password-protected PDFs. If a PDF asks for a password to open, the tool can't render it. Run it through the PDF Restriction Remover first if you have permission, or open it in a reader to remove the password.
  • Editing existing text. This tool adds annotations on top of the page — it does not change existing text in the PDF. To replace a paragraph, you would need to rebuild the document. PDF as a format is built around fixed positions and embedded fonts; in-place text editing is impractical even in desktop tools.
  • Scanned PDFs. Annotation works fine on scanned PDFs — they are images and your strokes draw cleanly on top. To extract the underlying text instead, use PDF to Text (OCR).
  • Highlight covers the text. The highlighter is a semi-transparent yellow rectangle drawn on top of the page. Some viewers render it darker than others. If readability suffers, switch to the Pen with a thinner stroke and underline instead.
  • Annotations look in the wrong place. Coordinates are stored in PDF page space, so resizing the browser between draw and save is fine. If the page renders rotated (some scanners produce sideways pages), rotate it first with PDF Rotator, then annotate.
Frequently asked questions
Are my files uploaded anywhere?
No. The PDF is read into your browser tab, rendered with pdf.js, and saved with pdf-lib — all client-side. Nothing is uploaded, stored, or logged. You can verify in your browser's DevTools Network tab: there is no request firing when you save.
Are the annotations real PDF annotations or just baked-in?
They are drawn into the page content. That means every PDF reader (Chrome, Preview, Acrobat, Firefox) shows them the same way — they are part of the file, not a separate layer that can be toggled off. The trade-off: they cannot be moved or removed afterward by another reader.
Can I edit the existing text in the PDF?
Not with this tool, and effectively not with any browser-based tool. Editing existing text means rewriting the PDF's content stream, which requires the original embedded fonts and a layout engine. Annotation-on-top is what most "PDF editor" web tools really do; this one is honest about it.
What about handwriting on a tablet?
Pointer events work for pen input — Apple Pencil, Surface Pen, drawing tablets are all supported. Press harder for thicker strokes is not implemented; pick a thickness from the toolbar instead.
Does it work on big PDFs?
Up to a few hundred pages, yes. Pages are rendered one at a time, so memory stays modest. For 500+ page documents on phones, expect slower page transitions — desktop browsers handle them without issue.
Can I save my annotations and come back later?
No — the annotations live in memory until you click Download. Refresh the tab or close the page and they are gone. Once downloaded, the annotated PDF is a normal PDF you can re-open in any reader, but the annotations are baked in by then, so you would need to add new ones from scratch.