🔲 PDF 裁剪Crop PDF

使用说明与常见问题How-to & FAQ

「PDF 裁剪」是什么？What is the Crop PDF tool?

裁剪 PDF 页面边距：按毫米设置上下左右裁掉的宽度并实时预览，或一键自动裁掉每页的白边，可只处理指定页码，适合去掉扫描黑边、放大阅读区域。Crop PDF page margins — set top/right/bottom/left in millimeters with a live preview, or auto-trim the white border on every page, optionally only for selected pages. Great for removing scan borders or enlarging the reading area.

如何使用「PDF 裁剪」？How do I use the Crop PDF tool?

在「PDF 裁剪」中，选择或拖入 PDF，填写「上」「右」「下」「左」要裁掉的边距（毫米），需要时填写页码范围，然后点击「裁剪并下载」。也可以勾选「自动裁白边（逐页检测）」，勾选后会出现「保留留白」，用来设置裁到内容后再留多少毫米。加密的 PDF 选好后会先出现「打开密码」栏和「打开」按钮。支持拖放文件。In the Crop PDF: Choose or drop a PDF, enter how much to trim from the Top, Right, Bottom and Left (mm), optionally a page range, then click "Crop & download". Or tick "Auto-trim white margins (per page)" — a "Keep padding" field then appears for the millimeters to leave around the content. For an encrypted PDF a Password field and an Open button appear first. Drag-and-drop is supported.

裁剪后被裁掉的内容还在吗？Is the cropped content really removed?

PDF 裁剪是设置页面的可见区域（CropBox），被裁部分在阅读器里看不到、打印也不会出现，但数据仍保存在文件里，可以被专业软件恢复。如需彻底删除敏感内容，请不要只依赖裁剪。PDF cropping sets the visible area (CropBox): cropped parts are hidden on screen and in print, but the data is still inside the file and specialised software can restore it. Don't rely on cropping to remove sensitive content.

“自动裁白边”是怎么工作的？How does auto-trim work?

工具在本地把每页渲染成图片，找出非白色内容的范围，再按你设置的留白距离裁剪，每页单独计算；页面背景不是白色时效果有限。Each page is rendered locally, the extent of non-white content is detected and the page is cropped to it plus your padding — computed per page. It works poorly if the page background isn't white.

页面是旋转过的怎么办？What if pages are rotated?

边距按你在阅读器里看到的方向（上下左右）计算，工具会自动换算旋转页面的实际坐标。Margins follow the orientation you see in a viewer; rotated pages are converted to their underlying coordinates automatically.

MediaBox 选项是什么？What does the MediaBox option do?

默认只改 CropBox（可见区域），这是最安全的做法；勾选后同时修改 MediaBox 等页面框，部分打印/排版软件会把页面当作更小的纸张。By default only the CropBox (visible area) changes, which is the safest choice. Ticking it also changes the MediaBox and related boxes, so print/layout software treats the page as a smaller sheet.

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 裁剪」免费吗？需要注册吗？Is the Crop PDF free? Do I need an account?

「PDF 裁剪」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 Crop 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.