PDF 加水印 - 免费为每一页添加文字水印

拖入一份 PDF，输入「CONFIDENTIAL」（或任意其他文字），位置保持为对角线，调整不透明度和颜色，然后「应用并下载」。水印会作为真正的 PDF 文本盖印到每一页上——可选中、在任意缩放级别下都矢量清晰——而非栅格化的叠加层。

八个位置外加对角线：左上、上中、右上、居中、左下、下中、右下（均为正向），以及对角线（旋转、放大、居中）。对角线是经典的防盗用水印；角落位置适合用作品牌标识或版本印记。

可以——水印是页面内容的一部分，而非阅读器端的装饰。它会随文档一起被打印、导出和截屏。要绕过它，就必须从头重新制作 PDF。

文字——我们使用 pdf-lib 的 drawText 以内嵌的 Helvetica Bold 标准字体进行渲染，因此可以无限缩放而不出现像素化，且只为文件增加极少的字节。若要在 PDF 上添加图片/Logo 水印，可先把 Logo 放在一个空白 PDF 的第一页，再将其合并到上层。

使用不透明度滑块——20-30% 通常是「可见但不抢眼」的最佳区间。颜色同样重要：30% 的浅灰在白色页面上呈现为柔和的水印，而红色或橙色即使在较低不透明度下也会吸引注意。

目前是全有或全无的——水印会应用到 PDF 的每一页。如需为部分页面添加水印，请先用我们的拆分 PDF 工具拆分 PDF，仅为需要的部分添加水印，然后再重新合并。

Yes — your PDF is uploaded over HTTPS to our secure server, where pdf-lib stamps the watermark on every page, and the file is deleted automatically right after processing. We never store, share or use your file for anything else, so it's safe for contracts, draft proposals and confidential client deliverables. If you need a tool that never uploads your file at all, use a desktop PDF editor instead.

免费、不限使用次数，水印上不带水印（我们不会添加自己的品牌标识）。所有设置都会保存在你的浏览器会话中，方便快速重复使用。

拖入你的 PDF，输入水印文字，选择位置（“对角线”可呈现经典的防复制效果，也可从八个角部/边缘位置中任选），设置不透明度、颜色和字号，然后点击“应用并下载”。第 1 页的实时预览会在你确认前精准呈现最终效果，相同的文字会被加印到每一页上。

Drag the Font size slider from 10pt up to 120pt — the live preview on page 1 updates instantly so you can see exactly how large the stamp will look before applying it to every page. Larger sizes (80pt+) suit a bold diagonal warning, while smaller sizes (20-30pt) work better for a discreet corner stamp.

Yes — the Rotation slider runs from -90° to 90° and is only active when Position is set to Diagonal, since corner and center positions stay upright to avoid running text off the page. The default -30° gives the classic anti-copy stamp look, but you can flatten it toward 0° for a more subtle tilt.

Each quick preset fills in both the watermark text and a matching colour in one click — CONFIDENTIAL in red, DRAFT in grey, COPY in blue, APPROVED in green and so on. It's a fast starting point you can still fine-tune afterward with the color picker, opacity slider or by typing your own custom text.

For a classic anti-copy watermark, use Diagonal position with rotation around -30°, opacity at 20-25% so the text stays readable, a neutral grey or muted red color, and font size 50-70pt. For subtler branding or version marking, switch to a corner position like Bottom-Right with a smaller font size (20-30pt) and slightly higher opacity.

Yes — click the color swatch to open the full picker: drag the saturation/hue square, type an exact hex code, or use the eyedropper (supported in Chrome and Edge) to sample a color straight off your screen, like from a logo. The 9 quick-pick presets next to it are just shortcuts and don't limit what color you can actually apply.