Add Watermark to PDF
Add text or image watermarks to PDF files online for free. Protect and label your documents client-side with 100% offline privacy.
Drag & drop your PDF files here
or browse local files
What is a PDF Watermark Tool?
Overview and core technical concepts
A PDF Watermark tool stamps custom text ('CONFIDENTIAL', 'DRAFT', 'DO NOT COPY') or logo image graphics diagonally or horizontally across PDF pages with opacity controls.
Why Watermark PDF Documents?
Key advantages, developer speedups, and security benefits
Protect Intellectual Property & Drafts
Stamp diagonal 'DRAFT' or 'CONFIDENTIAL' text to prevent unauthorized distribution of review copies.
Brand Official Documents
Embed subtle company logo watermarks on client proposals and invoices.
When Shouldn't You Use Diagonal Watermarks?
Anti-patterns, limitations, and when to choose an alternative approach
To add page numbers, use PDF Page Numbering.
Watermark Stamp Example
Sample inputs, expected outputs, and code patterns
Diagonal Text Watermark
Stamping 'CONFIDENTIAL' diagonally (-45°) at 25% opacity across all pages.Common PDF Watermark Mistakes
Frequent errors, security risks, and how to fix them
Frequently Asked Questions
A PDF watermark is an overlay layer (usually semi-transparent text or an image logo) applied on top of or behind existing PDF page content. Watermarks are typically used to protect copyrights, denote document statuses (like DRAFT or CONFIDENTIAL), prevent unauthorized sharing, or build corporate branding.
Text watermarks allow you to type custom words (e.g., 'CONFIDENTIAL' or 'DRAFT') and adjust standard fonts, sizes, colors, margins, and rotations. Image watermarks let you upload a PNG, JPG, WEBP, or SVG logo, scale its size, and position it at a specific layout anchor (like the Center or Top Right).
No, absolutely not. ToolZeno prioritizes user privacy. All PDF reading, rendering, watermark stamping, and saving actions execute completely inside your web browser sandbox memory. No file data is ever sent across the network or stored on any external server. You can even unplug your internet connection and the tool will work offline.
Yes. ToolZeno supports multiple scope targets. You can apply the watermark overlay to all pages, the first page only, the last page only, odd pages, even pages, or a customized page list and range (for example: '1-3, 5, 8-12').
We do not enforce any artificial file size limits. However, since all file modifications occur locally in browser memory, extremely large files (e.g., PDFs with hundreds of pages or over 100MB in size) might be restricted by your system's RAM. We recommend closing other background browser tabs when processing heavy documents.
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