PDF Watermarker & Stamper
Stamp contracts, NDAs, manuscripts, and reports with diagonal text warnings or brand logos. 100% client-side processing: your sensitive documents never leave your browser.
Drop your PDF here or click to browse
Supports single and multi-page PDFs up to 100MB. Processed safely inside your web browser.
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Why Watermark PDF Documents?
PDF (Portable Document Format) is the global standard for business agreements, financial statements, pitch decks, legal filings, and educational coursework. However, once an unprotected PDF is shared via email or cloud drives, it can be distributed, leaked, or copied without credit or authorization.
Legal Contracts & NDAs
Ensure unexecuted agreements are prominently stamped as «DRAFT» or «CONFIDENTIAL» to prevent premature signature or disclosure disputes.
Course Creators & Authors
Protect paid ebooks, worksheets, and syllabus PDFs from being shared on file-sharing sites and unauthorized forums.
B2B Sales & Financial Proposals
Personalize quotes or business plans with client names or transaction IDs to deter forwarding to competitors.
Architectural & Design Blueprints
Overlay diagonal copyright seals across schematic drawings to ensure attribution before full payment clearance.
How to Watermark a PDF in 3 Simple Steps
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1
Upload Your Document
Drag and drop your PDF file into the dropzone. Your file is read locally into browser memory using the HTML5 File API.
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2
Customize Your Stamp & Style
Select a quick preset (like CONFIDENTIAL or DRAFT) or type custom text. Fine-tune rotation angle, font size, opacity, and choose between single center stamp or full-page tiled repeat.
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3
Stamp & Download
Click "Stamp & Download PDF". The newly watermarked file is rendered immediately and saved directly to your Downloads folder.
Frequently Asked Questions
No, absolutely not. Unlike standard online converters that upload your confidential files to remote servers, Watermark Ninja performs the entire PDF modification inside your web browser using JavaScript (PDF-Lib). Your files never leave your computer, making it 100% compliant with strict enterprise confidentiality and GDPR standards.
Yes! You can choose to apply the watermark across all pages, only on the first page, on odd/even pages, or specify a custom page range (e.g. pages 1-5, 10).
A Center Stamp places one prominent diagonal mark across the center of each page. A Tiled Grid repeats the text at regular diagonal intervals across the entire sheet, ensuring that even if someone takes a partial screenshot or crops a section, the watermark remains clearly visible.
Yes, switch to the "Logo / Image Stamp" tab to upload your transparent PNG or JPG seal. You can adjust the opacity, scale, and placement (Top-Right, Center, Bottom-Right, etc.).
Yes, Watermark Ninja PDF Stamper is 100% free with no registration, no page limits, and no hidden subscriptions.