PDF Watermark

What the PDF Watermark Does

This tool overlays a text watermark on a PDF. It draws your chosen word or phrase large and diagonal across the middle of each page, faint enough to read the content underneath but clear enough to mark the document's status.

It is the quick way to label a PDF as a draft, confidential, a sample or a copy, so anyone who sees or prints it understands how it should be treated.

How It Works

The tool opens the PDF, embeds a bold standard font, and for each page draws your watermark text across the centre at a 45-degree angle, in grey at about thirty percent opacity. The low opacity lets the underlying content show through while the watermark stays visible.

The watermark is drawn onto the page content, so it becomes part of each page. It is applied to every page in one pass, and the watermarked file is saved for download. It marks the document visibly, but it does not encrypt or lock it.

Processing pipeline

1. Open the PDF. Load the document and embed a bold font.
2. Take your text. Use the watermark text you enter, such as CONFIDENTIAL.
3. Stamp each page. Draw the text diagonally across the centre of every page, semi-transparent.
4. Save the file. Save and download the watermarked PDF.

What it stamps

The watermark is drawn onto the page, so it is visible and prints, but it is not tamper-proof — it can be removed by re-processing the PDF. It is a deterrent, not document security.

Privacy

The PDF stays on your device. It is read, the watermark is drawn, and the new file is generated locally — no upload, and no copy kept anywhere.

Nothing is stored and there is no account. Refresh or close the tab and both the original and the watermarked file are cleared from memory — fine for private documents.

Standards & references

• Visible overlay — The watermark is text drawn onto the page at low opacity, so it shows over the content and appears in print. It marks the document's status clearly to anyone who views it.
• A deterrent, not security — Because it is drawn onto the page rather than encrypting it, the watermark can be removed by re-processing the PDF. It discourages casual misuse but does not protect or lock the document.
• Applied to every page — The text is stamped on all pages in one pass, diagonally across the centre, so the whole document is marked consistently rather than just the first page.

Accuracy & Limitations

As a visible mark the result is clear and consistent: your text appears diagonally across every page, faint enough to read the content beneath but unmistakable as a label.

It is not tamper-proof. The watermark is part of the page image and can be removed by someone who re-processes the PDF, so it deters casual copying but does not secure the document. For real protection, encryption or rights management is needed.

The position is centred and the size is fixed. Very long watermark text may extend beyond the page, and very short text sits small in the middle, since the placement is a simple centre estimate rather than a precise fit.

It draws text only. There is no image or logo watermark, no tiling across the page, and no per-page text — the same word or phrase is stamped on every page in the same way.

Real-World Use Cases

When to use it — and when not to

For genuine protection, use PDF encryption or rights management, which actually restricts the file. For a logo or tiled watermark, a full PDF editor offers more. This tool adds a visible text watermark as a deterrent.

Frequently Asked Questions

References

• pdf-lib — PDF library
• Digital watermarking (Wikipedia)
• Portable Document Format (Wikipedia)

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