Watermark PDF
Add text or image watermark to your PDF pages. Your files are processed in your browser - nothing is uploaded to any server.
Add Watermark to PDF - Free Online Tool
A watermark is a text label or image drawn directly onto each PDF page, communicating ownership, document status, or confidentiality at a glance. This tool uses pdf-lib, a JavaScript library running entirely in your browser, to embed the watermark into the PDF page content. Your file is read by the browser File API and never sent to any server - the entire operation happens on your device.
Why Watermarking Your PDF Matters
Watermarks serve practical purposes across industries. Here is why professionals label their PDFs before sharing:
- Ownership and authorship: A visible label signals who created the document, discouraging unauthorized reuse or redistribution.
- Document status: Marking a file as "Draft," "Approved," or "For Review" reduces confusion in collaborative workflows.
- Brand visibility: Companies embed logos or company names to reinforce identity in every shared file.
- Legal protection: A watermark can serve as evidence of original ownership in disputes over intellectual property.
- Deterring unauthorized copying: Even a semi-transparent overlay makes unauthorized reproduction more obvious and less appealing.
For deeper document security beyond visual labeling, you may also want to password protect your PDF or permanently redact sensitive content before sharing.
How the Watermark Is Applied
The watermark is drawn directly into each PDF page's content stream, not stored as a separate annotation layer. This means it cannot be selected, moved, or deleted with standard PDF editors the way a comment or signature field can be. Text watermarks are rendered using Helvetica, one of the 14 standard fonts built into every PDF viewer, so no font data needs to be embedded and the file size increase is minimal. Image watermarks are embedded into the PDF once as a shared image object and referenced by each watermarked page, rather than duplicated per page. Opacity is applied through the PDF graphics state, which controls how much of the underlying page content shows through the watermark. Because the entire process runs in your browser, your file never leaves your device.
How to Add a Watermark to a PDF
- Upload your file: Click the upload area or drag and drop your PDF. The file is loaded into browser memory using the File API - nothing is uploaded to any server.
- Choose watermark type: Select text or image. Text watermarks accept any custom string. Image watermarks accept PNG and JPG files.
- Customize appearance: Set font size, color, opacity (0-100%), rotation, and position (center, top-left, top-right, bottom-left, bottom-right).
- Choose pages: Leave the pages field empty to watermark all pages, or specify individual pages or ranges such as 1, 3, 5-7.
- Download: Click Add Watermark. pdf-lib processes the file in your browser and the watermarked PDF is saved to your device.
When Should You Use a PDF Watermark?
- Sending a proposal or quote to a client before final approval
- Distributing internal reports that should not leave the organization
- Sharing design mockups or photography portfolios for client review
- Publishing academic or research drafts before peer review completion
- Issuing certificates or official documents that need an authenticity marker
If your document also requires a signature, combine watermarking with our PDF signing tool to finalize and authenticate the file in one workflow.
Watch How It Works
Prefer a visual walkthrough? The short video below demonstrates how to stamp your document using our online tool, covering the key options and settings available to you.
FAQ
The watermark is drawn directly into the PDF page content stream, not added as a separate annotation object. This makes it part of the page itself rather than an overlay that can be independently selected or removed. Text is rendered using Helvetica with the specified size, color, and opacity. Image watermarks are embedded as a PDF image object and drawn at the specified position and opacity. The process runs entirely in your browser - no server is involved.
No. The watermark is applied entirely in your browser using pdf-lib, a JavaScript PDF library. Your file is loaded into browser memory via the File API and processed on your device. No bytes are transmitted to any server at any point during the process.
Yes. Switch to image mode and upload a PNG or JPG file. The image is embedded into the PDF as a shared image object and scaled to fit within 50% of the page dimensions, preserving the aspect ratio. You can adjust the opacity and position the same way as a text watermark.
Yes. Enter individual page numbers or ranges in the pages field before applying. For example, entering 1, 3, 5-7 watermarks pages 1, 3, 5, 6, and 7. Leave the field empty to apply the watermark to every page. Pages not included in the selection are passed through to the output unchanged.
The original text, images, and formatting of the document are not modified. The pages from the source document are copied into a new PDF and the watermark is drawn on top of each selected page's content stream. The source file on your device is never changed. The downloaded file is a new PDF with the watermark added.
Because the watermark is drawn directly into the page content stream rather than stored as a separate annotation object, it cannot be selected or deleted with standard PDF editors. Removing it would require editing the PDF content stream directly or using image-based redaction tools, which is a complex operation that may also affect surrounding content. Always keep the original file before applying the watermark if you need a clean version later.
Text watermarks are rendered using Helvetica, one of the 14 standard PDF fonts that are built into every PDF viewer and require no embedding. This keeps the output file size small and ensures the watermark text renders consistently across all PDF readers without font substitution.
Text watermarks add a small amount of data to each page's content stream - typically a few hundred bytes per page - so the size increase is negligible. Image watermarks embed the image file as a PDF image object, which is shared across all pages it appears on. The size increase depends on the image file size, but the image is embedded once and referenced by each page rather than duplicated.
Removing a watermark from a document you do not own or have rights to modify can be illegal, particularly when the document contains copyrighted material. In many jurisdictions, stripping an ownership or authorship mark without permission may violate intellectual property law. Always confirm you have the right to modify a document before attempting to alter or remove any embedded labels.
Opacity is set as a parameter in the PDF graphics state when the watermark is drawn onto the page. A value of 100% is fully opaque, completely covering the content behind it. Lower values allow the page content to show through. For most use cases, an opacity between 20% and 40% produces a clearly visible but non-obstructive watermark that does not interfere with reading the document.