PDF Watermark & Page Numbers
Use this free online PDF Watermark tool to add a custom text or image watermark to every page of any PDF. It is useful for marking a document as Draft, Confidential or Sample before sending it externally, branding a deliverable with your company logo, deterring unauthorised redistribution, or stamping invoice copies with their version. Drop the PDF into the upload zone, type the watermark text or upload an image, set the opacity, position and rotation, and download the watermarked file. Watermarking runs in your browser using pdf-lib — your documents never leave your device. The original file stays unchanged; only the new file is altered.
Click to choose or drag & drop a PDF
How to Use This PDF Watermark
Adding a watermark takes a drop, a few options and a click.
- Drop the PDF into the upload zone or click to choose a file.
- Pick the watermark type — text or image — and enter the text or upload the image.
- Set the opacity (40-60% is common), the position (centre, diagonal, header, footer) and the rotation angle.
- Optionally tick 'apply to first page only' or 'apply to every page'.
- Click Add Watermark, then Download to save the watermarked file; the original is untouched.
How This PDF Watermark Works
Watermarking superimposes a graphic or text element over every page of a PDF without modifying the underlying content stream. The tool uses pdf-lib in your browser to load the input PDF into an object model, then walks the page tree and adds a new content stream entry per page that draws your chosen watermark. For text watermarks the engine uses one of the standard PDF fonts (Helvetica by default) and draws the string at the requested font size, opacity, rotation and position. For image watermarks the uploaded PNG or JPG is embedded as a PDF XObject and drawn the same way. Opacity is implemented via the PDF graphics state's CA/ca extended graphics parameters, which gives consistent results across every reader. Rotation is applied via a coordinate transformation matrix so a diagonal Confidential stamp lands exactly at 45 degrees regardless of page size. Because the watermark is added as an overlay rather than baked into the original images, the underlying text remains selectable and searchable. Everything happens locally in the browser, which keeps confidential documents private and removes the upload limits of online services.
Last updated: May 2026.
Frequently Asked Questions
Can the watermark be removed?
A determined user could re-render or convert the PDF and try to clean it up, but that's expensive and the watermark stays in the file as drawn. For tamper-evidence, also lock the PDF's permissions.
Why is the diagonal watermark not perfectly centred?
Rotating text shifts its bounding box. The tool uses an offset for typical font metrics, but extra-long watermarks may need manual adjustment via the size slider.
Can I use an image as the watermark?
Not directly with this tool — only text watermarks are supported. For image watermarks, use a desktop tool like Acrobat.
What page-number format should I use?
"1 of N" is best for printed documents (helps detect missing pages). "Page 1" is more conversational. Plain numbers are minimal and best for documents with their own headers.
Will the watermark print?
Yes — it's embedded in the PDF as drawn page content, so it appears on screen and in print exactly the same.