PDF 水印

给 PDF 页面添加文字或图片水印

将 PDF 文件拖放到此处，或点击浏览

选择 PDF 文件

最大文件大小：128 MB

你的文件完全在浏览器中处理，不会上传到任何服务器。

向 PDF 添加机密水印 — 加盖敏感文档

Stamp 'CONFIDENTIAL', 'DRAFT', 'INTERNAL USE', or custom text diagonally across every page of a PDF to mark it as sensitive. Our browser-side tool uses pdf-lib to overlay the watermark — your documents stay on your device. Customizable color, opacity, font, and rotation.

100% FreeNo UploadNo Sign-upMulti-Page Diagonal Stamp

使用步骤

Upload Your PDF: Drag the sensitive PDF in. Multi-page documents are supported — the watermark is applied to every page consistently. PDFs up to 500 MB and 1000+ pages work without upload.
Customize Watermark: Type the watermark text (default: 'CONFIDENTIAL'). Choose color (red is conventional; gray is subtle), opacity (10-30% is typical), font size, rotation (45° is the classic diagonal; horizontal works for header-style marks), and page placement (diagonal, top, bottom, custom position).
Position & Apply: Click 'Add Watermark'. pdf-lib overlays the watermark on every page in your browser via WebAssembly. A 50-page document stamps in under 5 seconds.
Download Stamped PDF: Save the watermarked PDF. The watermark is flattened into the page (not a separate layer that can be removed easily), but it doesn't modify any original content — your text, images, and layout are unchanged.

为什么选择此工具

100% Local Processing: Files are processed entirely in your browser using JavaScript — never uploaded to any server.
No Limits: No file count or file size restrictions. Process as many files as your device can handle.
No Sign-up: Free forever, no account needed, no email required. Open the page and start.
Private by Design: Nothing is sent to any server. Close the tab and your files are gone forever.

常见问题

How do I mark a PDF as confidential?

Open our PDF Watermark tool, drop your PDF, type 'CONFIDENTIAL' (or any custom text), and pick your style — diagonal in red is the most common. Click 'Add' and your PDF is watermarked. The mark is visible on every page and (by default) flattened into the page content.

Does the watermark look professional?

Yes — we use crisp vector text (any system font), accurate rotation, and adjustable opacity. The classic look is 45° diagonal, red, 25% opacity across the center of each page. For headers, choose horizontal small text top-right or bottom-center with low opacity.

Can the watermark be removed?

Flattened watermarks (default) become part of the page content — they can't be removed without re-OCR'ing or re-rendering the entire page. Layer-based watermarks (selectable in advanced settings) can be removed by recipients via Adobe Pro. Use flattened for sensitive documents; use layered for visible branding that doesn't need to be permanent.

Will my PDF be uploaded?

No. pdf-lib processes everything in your browser. Whether your PDF contains attorney-client privileged information, M&A deal materials, or HR records, the file stays on your device. Ideal for confidential workflows.

Can I add multiple watermarks (e.g. CONFIDENTIAL + DRAFT)?

Yes — drop multiple watermarks in our tool. Each is rendered independently and stacked on the page. Useful for combining classifications (e.g. 'INTERNAL' + 'DRAFT v2'), adding date stamps, or appending page numbers as text watermarks.

Does it support image watermarks (logos)?

Yes — for company logos or graphic watermarks, switch to 'Image Watermark' mode and upload a PNG with transparency. We then stamp the logo across pages with adjustable size, position, and opacity. This is the 'Watermark with Logo' scenario — see our other tools.