This PDF watermark tool stamps a diagonal text watermark, such as CONFIDENTIAL or DRAFT, across every page of your document in a single pass. Type the words you want, tune the font size and opacity, and the tool applies the overlay at a fixed 45-degree angle for a clean, consistent look. It is handy when you need to add a watermark to a PDF before sharing drafts, mark internal contracts, or label sample documents. Designed for developers, legal and QA teams, and anyone who wants a quick confidential stamp on a PDF without desktop software. Every page is processed locally in your browser, so your files stay on your machine and nothing is uploaded to a server. The diagonal text watermark is drawn directly into the page content using a bold Helvetica face for reliable rendering everywhere.
Features
Stamps a diagonal text watermark onto every page in one click
Custom watermark text with a CONFIDENTIAL default placeholder
Adjustable opacity slider from 5% to 100% for subtle or bold marks
Adjustable font size from 10 to 200 points to fit page and text length
Fixed 45-degree diagonal angle for a consistent look
Bold Helvetica rendering embedded into the page content
Centers the watermark automatically on each page
Runs entirely in your browser with no upload of your PDF
How to use the Watermark PDF
Drop or select the PDF you want to watermark.
Type your watermark text in the input, for example CONFIDENTIAL.
Set the size and drag the opacity slider to the visibility you want.
Click Add watermark & download to stamp every page.
Save the downloaded file and keep your original for an unmarked copy.
contract.pdf → contract-watermarked.pdf with a diagonal CONFIDENTIAL stamp at 45° on every page
Stamping a 60-point CONFIDENTIAL mark at 20% opacity across all pages.
Common errors & troubleshooting
The Add watermark button stays disabled. — Enter some watermark text first; the tool needs non-empty text before it can stamp the pages.
The watermark is too faint to read. — Raise the opacity with the slider and increase the font size so the text stands out against the page.
Long watermark text runs off the page edges. — Shorten the phrase or lower the font size so the rotated text fits within the page width.
You need an unmarked copy after stamping. — The watermark is drawn into the page content and cannot be peeled off, so always keep your original file.
The PDF will not open in the tool. — Make sure the file is a valid, unencrypted PDF; password-protected files must be unlocked before watermarking.
Frequently asked questions
What is the PDF Watermark tool?
It is an in-browser tool that stamps a diagonal text watermark, such as CONFIDENTIAL or DRAFT, onto every page of a PDF with the size and opacity you choose.
How do I add a watermark to a PDF?
Open the PDF Watermark tool, type your text such as CONFIDENTIAL, set the size and opacity, then click Add watermark & download to stamp every page and save the result.
Can I change how visible the watermark is?
Yes. Use the opacity slider from 5% to 100% for a subtle background mark or a bold, prominent stamp, and adjust the font size to match.
Can the PDF watermark be removed later?
No. It is drawn into the page content, so keep your original file if you ever need an unmarked copy.
Does it watermark every page or just the first?
The text is stamped on every page of the document at the same 45-degree diagonal angle, centered on each page.
Is my PDF uploaded anywhere when I watermark it?
No. The PDF Watermark tool processes your file locally in your browser, so your document never leaves your device.
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