Add Watermark to PDF

No. Every part of watermarking — reading your PDF, drawing the watermark text onto each page, and rendering the preview — happens entirely inside your browser using the pdf-lib and pdf.js JavaScript libraries, with no server-side component involved at any point. This means you can safely watermark confidential contracts, unreleased drafts, or internal reports without any of that content ever leaving your device. You can verify this yourself by watching your browser's network tab while you use the tool — you won't see any outgoing requests carrying PDF data, and the tool keeps working with no internet connection once the page has loaded.

Center Diagonal places a single instance of your watermark text across the middle of each page at a 45-degree angle — the classic look for marking a document CONFIDENTIAL or DRAFT in a way that's clearly visible but doesn't obscure any single area of content too heavily. Top and Bottom place a single horizontal instance of the text near the top or bottom edge of each page — useful for a subtler stamp, like a company name or a 'Sample — Not for Distribution' notice, that doesn't overlap your main content at all. Tiled ignores the position setting and instead repeats the watermark text in a diagonal grid pattern across the entire page — the strongest deterrent against unauthorized copying or redistribution, since cropping or covering any one instance still leaves the rest of the page marked.

The watermark text is drawn as a new layer on top of the existing page content, and your original content — text, images, vector graphics — is left completely untouched underneath it; nothing is deleted, moved, or re-rendered. Using a low opacity (this tool defaults to 30%) keeps the underlying content fully readable through the watermark, which is standard practice for document watermarking. If you want the watermark to be more of a deterrent than a subtle mark, increasing the opacity toward 100% makes it much more prominent, at the cost of being more visually intrusive over your content.

It stays as real, vector-based PDF text — this tool uses pdf-lib's native text-drawing capability, embedding a standard font and drawing your watermark string directly as text objects on the page, the same way any other text in a PDF is stored. This means the watermark renders crisply at any zoom level (unlike a rasterized image watermark, which can look blurry when zoomed in), and while it's technically extractable/selectable like any PDF text, it visually and functionally serves as a proper watermark layered over your content.

Not directly through this tool — once a watermark is applied and you download the result, that PDF permanently includes the watermark as part of its page content, the same way it would if you added it in any other PDF editor. If you need an unwatermarked version later, keep your original file before watermarking, since the watermarking process here (like most watermarking tools) is intentionally one-directional — reversibility would defeat the purpose of a watermark as a deterrent or provenance mark in the first place.

This tool can open and watermark many encrypted PDFs automatically, since the underlying library is configured to ignore standard PDF encryption when reading a file's pages. Some PDFs use encryption or permission restrictions strong enough that a browser-based tool genuinely cannot open them without the correct password. If your file fails to load, the most reliable fix is to remove its password protection first using your PDF viewer's 'remove security' option, then watermark the now-unprotected file normally.

Nothing is retained anywhere. Because watermarking happens entirely in your browser's memory with no server storage, database, or persistent browser storage involved, closing the tab, refreshing the page, or navigating away immediately and permanently discards your uploaded file and any watermarked result you haven't yet downloaded. Make sure to download your watermarked PDF before leaving the page.

The Center Diagonal and Tiled positions calculate the watermark's placement based on each page's actual dimensions, so a very wide page (like a landscape-oriented spreadsheet export) will show the diagonal watermark angled the same 45 degrees but positioned relative to that page's own center — which can look proportionally different from a standard portrait page. This is expected and consistent behavior; the watermark always centers correctly relative to each individual page's own size, even in a PDF that mixes page orientations or dimensions.