Knackpad

Redact PDF Free — No Upload, No Sign Up

Draw black boxes over sensitive text, signatures, or images. Choose solid black or a custom [REDACTED] label. Multi-page. Undo. Zoom. Permanently embedded — not just a visible layer.

🔒 100% browser-only — your file never leaves your device
📄
Drop your PDF here

or click to choose — processed entirely in your browser

0
redactions across 0 pages
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Mode
✎ How to redact: Click and drag a rectangle over any area to mark it. Redactions appear as overlays — use Ctrl+Z to undo, arrow keys to change pages, +/- to zoom. Click Download Redacted PDF when done — marks are permanently embedded as filled shapes.
Building redacted PDF…

How it works

  1. 1
    Your PDF is read using the browser's FileReader API — it stays entirely on your device and is never sent to any server. You can confirm this by opening browser DevTools → Network tab and verifying zero outgoing file uploads.
  2. 2
    PDF.js (Mozilla) renders each page to a <canvas> element at your chosen zoom level. The original PDF bytes are kept separate and untouched until you download.
  3. 3
    You drag rectangles over sensitive areas. Each rectangle's position is stored in PDF coordinate space (bottom-left origin, measured in points at 72 pt/inch). The tool converts from canvas pixels to PDF points using the page's viewport dimensions.
  4. 4
    Choose your redaction style: Black fill (standard), White fill (clean erase), or [REDACTED] label with a solid black bar and white text drawn using pdf-lib's text rendering in Helvetica. Custom labels let you specify any text (e.g. [CONFIDENTIAL], [PII REMOVED]).
  5. 5
    On download, pdf-lib opens the original bytes and draws permanent opaque filled rectangles (and optional text) into the PDF content stream using drawRectangle and drawText. The resulting file is downloaded to your device — nothing is retained.

Frequently asked questions

Completely private. The tool uses only browser-local APIs (FileReader, Blob, URL.createObjectURL). Both PDF.js and pdf-lib run as local JavaScript in your browser tab. No network request is made with your file data. You can verify this: open DevTools → Network tab → filter by "XHR/Fetch" — you will see zero requests containing your PDF bytes while using this tool.
The black (or white) rectangles are embedded as opaque filled shapes directly in the PDF content stream — they are not an annotation layer or a togglable overlay. However, this tool draws shapes on top of the page content; it does not strip the underlying text data from the PDF's internal text layer. For everyday use (blocking personal details, phone numbers, addresses before sharing), this approach is standard and effective. For maximum legal or medical compliance where underlying text must also be removed, consider a dedicated professional tool like Adobe Acrobat Pro's full redaction workflow, which additionally purges text data from the content stream.
Black fill — draws a solid black rectangle. Standard redaction appearance used in legal and government documents.

White fill — draws an opaque white rectangle. Useful for cleanly removing content in white-background documents without a visible redaction marker.

[REDACTED] label — draws a solid black bar with white "[REDACTED]" text centered inside. Commonly used in legal discovery and FOIA documents to indicate intentional removal.

Custom label — same as the label mode but with text you specify (e.g., [CONFIDENTIAL], [PII REMOVED], [ATTORNEY-CLIENT PRIVILEGE]).
Yes. Use the ← Prev / Next → buttons (or keyboard arrow keys) to navigate between pages. Redactions on each page are tracked and listed independently. The total count shown at the top reflects all redactions across all pages. When you download, every page's redactions are applied before the file is saved.
PDF coordinates use a bottom-left origin and are measured in points (1 pt = 1/72 inch). The canvas uses top-left pixel coordinates. This tool converts between the two systems using the rendered page dimensions. A small visual offset can occur on PDFs with non-standard crop boxes or rotated pages. To be safe, draw each rectangle slightly larger than the content you want to cover. Using the zoom-in feature helps you draw with greater precision.
Only PDF files (.pdf) are supported. There is no server-side size limit — the constraint is your browser's available memory. Modern browsers typically handle PDFs up to 200–300 MB without trouble. Very large PDFs with many high-resolution images may be slower to render between pages. Output file size is generally similar to input since only the page content stream is modified.