💧 PDF 加水印Add Watermark to PDF

使用说明与常见问题How-to & FAQ

「PDF 加水印」是什么？What is the Add Watermark to PDF tool?

给 PDF 批量添加文字或图片水印：支持中文、多行文字、颜色、透明度、旋转角度，可放在中间、角落或平铺满页，也可置于内容下方，只处理指定页码，全部在本地完成。Stamp a text or image watermark on PDF pages — Chinese and multi-line text, color, opacity and rotation, placed in the centre, a corner or tiled across the page, optionally beneath the content and only on selected pages. All done locally.

如何使用「PDF 加水印」？How do I use the Add Watermark to PDF tool?

在「PDF 加水印」中，按需设置「类型」、「水印文字」、「字号（0=自动）」、「颜色」、「水印图片（PNG/JPG）」等选项，然后点击「添加水印并下载」按钮即可。支持拖放文件。加密的 PDF 选好后会先出现「打开密码」栏和「打开」按钮，输入密码点「打开」后再继续。In the Add Watermark to PDF: Set "Type", "Text", "Font size (0 = auto)", "Color", "Image (PNG/JPG)", then click "Add watermark & download". Drag-and-drop files is supported. For an encrypted PDF, a Password field and an Open button appear after you choose it — enter the password and click Open first.

可以添加中文水印吗？Can I use a Chinese watermark?

可以。检测到中文等非拉丁字符时会自动加载内置的思源黑体（Noto Sans CJK）子集并只嵌入用到的字，生成的水印文字仍可被搜索和复制。Yes. When Chinese or other non-Latin characters are detected, a built-in Noto Sans CJK subset loads automatically and only the glyphs used are embedded, so the watermark text stays searchable.

“置于内容下方”有什么用？What does "Behind content" do?

水印会画在页面原有内容的下层，文字不会被遮挡、看起来更自然；但如果页面有不透明的白色背景或整页图片（如扫描件），水印会被盖住而看不到。The watermark is drawn beneath the existing page content so text isn't covered and it looks more natural. If the page has an opaque white background or is a full-page image (like a scan), the watermark will be hidden.

水印可以被去除吗？Can the watermark be removed?

水印作为页面内容写入 PDF，普通阅读器无法删除，但专业的 PDF 编辑器仍可能删除或编辑。需要更强的保护时，可先加水印再用“PDF 扁平化”整页栅格化，或配合“PDF 加密”限制编辑。The watermark becomes part of the page content and can't be removed in ordinary viewers, but professional PDF editors may still edit it. For stronger protection, rasterize with Flatten PDF afterwards or restrict editing with Protect PDF.

字号设为 0 是什么意思？What does font size 0 mean?

自动根据页面尺寸计算字号：居中时文字长度约为页面较短边的 90%（旋转 45° 时沿斜线摆放，看起来约占页宽的六七成），角落位置约 40%，平铺约 30%；需要精确大小时请手动填写字号，例如平铺用 24。The size is calculated from the page: centred text is about 90% of the page's shorter side long (at 45° it runs diagonally, so it looks like roughly 60–70% of the width), about 40% in a corner and 30% when tiled; enter a size manually for exact control, e.g. 24 for tiled.

加密的 PDF 可以处理吗？Can it handle password-protected PDFs?

可以。如果 PDF 需要打开密码，会提示你输入；只有权限限制（无打开密码）的文件会自动打开。输出文件不再带密码，如需加密请使用“PDF 加密”工具。Yes. If the PDF needs an open password you'll be asked for it; files with only permission restrictions open automatically. The output is not password-protected — use the Protect PDF tool if needed.

文件会上传到服务器吗？Are my files uploaded?

不会。PDF 在你的浏览器里用 pdf-lib / pdf.js 处理，文件不会离开你的设备，关闭页面后不留存任何数据。No. The PDF is processed in your browser with pdf-lib / pdf.js; files never leave your device and nothing is kept after you close the page.

「PDF 加水印」免费吗？需要注册吗？Is the Add Watermark to PDF free? Do I need an account?

「PDF 加水印」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Add Watermark to PDF is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.