Drop your PDF here
or click to browse
PDF files up to 100 MB · Processed entirely in your browser
How it works
- 1
Upload your PDF
Drop your PDF onto the tool or click to browse. Your file is loaded locally — nothing is sent anywhere.
- 2
Configure the watermark
Set your watermark text, then adjust opacity, colour, rotation, and size. A live preview shows the effect.
- 3
Apply and download
Click Apply and instantly download a new PDF with your watermark on every page.
Why use this watermark tool?
100% private
Your PDF is processed locally using pdf-lib. Nothing is ever sent to our servers.
Instant, no sign-up
No account or email needed. Upload, customise, and download in seconds.
Fully customisable
Control the text, opacity, colour, rotation, and size of your watermark.
Live preview
See an approximate preview of the watermark before applying it to the PDF.
Applied to all pages
The watermark is stamped on every page of the document automatically.
One-click download
The watermarked PDF is ready to download immediately — no email, no wait.
When would you watermark a PDF?
Watermarks serve both legal and practical purposes. Here are the most common reasons to stamp a PDF before sharing it.
Mark confidential documents
Adding "CONFIDENTIAL" or "PRIVATE" to internal reports, financial statements, or legal drafts signals to recipients that the content should not be forwarded or shared.
Label draft versions
Stamp "DRAFT" on proposals, contracts, or design briefs sent for review. It prevents recipients from treating preliminary versions as final.
Mark invoices as paid
Overlay "PAID" on invoices before archiving or forwarding to clients, making the payment status immediately visible without editing the document.
Assert copyright on content
Add your name, company, or copyright notice to PDFs containing original writing, designs, or research before distributing them publicly.
Personalise shared copies
Stamp each copy of a document with the recipient's name or organisation. If the document is leaked, you can trace which copy was shared.
Indicate sample or preview
Add "SAMPLE" to previews of paid content, templates, or reports you share before purchase, making it clear the full version requires a licence.
How PDF watermarking works under the hood
No servers, no uploads — here is exactly what happens when you add a watermark to a PDF in your browser.
- 01
Your PDF is read locally
When you upload a file, the browser reads it from disk using the File API. The raw bytes are held in memory and never sent over the network — your document stays entirely on your device.
- 02
pdf-lib parses the document structure
The open-source pdf-lib library loads the raw PDF bytes in JavaScript, understanding its internal page tree, fonts, and content streams. No server-side processing is involved at any point.
- 03
A font is embedded for the watermark
pdf-lib embeds the Helvetica Bold font into the PDF. This ensures the watermark text renders consistently on every device and PDF viewer, regardless of what fonts the reader has installed.
- 04
Text is drawn onto every page
For each page, pdf-lib calculates the page dimensions, scales the font size proportionally, centres the text, and draws it at the specified opacity, colour, and rotation angle. This is a vector drawing operation — the text is crisp at any zoom level.
- 05
The result is downloaded instantly
The modified PDF is serialised to bytes entirely in memory and wrapped in a Blob. Your browser triggers a standard file download — no server roundtrip, no expiring link, no waiting.
Choosing the right watermark settings
The best watermark depends on how the document will be shared and what it needs to communicate. Here is a quick guide.
| Setting | Lower / smaller value | Higher / larger value |
|---|---|---|
| Opacity | Subtle — readers see the content clearly, watermark is a background hint | Bold — watermark is prominent and hard to ignore |
| Size | Small text fits neatly in the centre without covering content | Large text dominates the page — best for "DRAFT" or "SAMPLE" warnings |
| Rotation: −45° | — | Diagonal text is the most recognisable watermark style and hardest to crop out |
| Rotation: 0° | — | Horizontal text reads more naturally — good for short stamps like "PAID" |
| Color: Gray | — | Neutral and professional — least distracting on colour documents |
| Color: Red | — | High-visibility — ideal for urgent notices like "VOID" or "REJECTED" |
Tips for effective PDF watermarks
A well-placed watermark protects your document without making it unreadable. Here is how to get the balance right.
Keep opacity between 20–40% for readability
Very high opacity watermarks can make the underlying text difficult to read. For documents that recipients need to review carefully — like contracts or reports — keep opacity low so the content remains clear.
Use short, uppercase text
Single-word watermarks like "CONFIDENTIAL", "DRAFT", or "PAID" are universally understood and render cleanly at any size. Long sentences wrap unexpectedly and may obscure important content.
Understand that watermarks are not security
A text watermark embedded by this tool is a visual deterrent, not a security lock. A determined user could potentially edit or remove it with PDF editing software. Combine watermarks with PDF password protection for stronger access control.
Test-print before bulk distribution
Screen colours and printer output can differ, especially for subtle grey watermarks. Print one test page to check the watermark is clearly visible at the size and colour you chose before distributing widely.