Cropping a PDF page trims what's visible — removing unwanted margins, cutting off a header or footer, or isolating a specific section of a page. It's a common need and there are several ways to do it depending on what tools you have available.
One Thing Worth Knowing First
PDF cropping adjusts the CropBox — the defined visible area of a page — but doesn't permanently delete the content outside that area. The hidden content is still in the file; it's just not shown. This matters if you're cropping for privacy reasons (removing a watermark or header with confidential information): anyone who opens the PDF in a tool that ignores the CropBox, or who examines the file's internal structure, can still access the hidden content. For privacy-sensitive cropping, you need a tool that actually removes the content from the file, not just hides it.
Cropping in Adobe Acrobat Pro
Acrobat Pro has the most precise crop control. Go to Tools → Edit PDF → Crop Pages. Draw a crop rectangle on the page, then double-click inside it to open the Crop Pages dialog where you can set exact margins numerically. You can apply the crop to the current page, a range of pages, or all pages at once — useful when you need to trim the same margin from an entire document.
Cropping With a Browser Tool
WukongPDF's PDF Editor includes a crop tool that works in any browser without installation. Upload the PDF, select the crop function, drag the crop handles to define the area you want to keep, and download. This is the fastest free option for cropping one or a few pages and doesn't require any software.
Browser-based crop tools are fine for visual cropping where you're working by eye. For precise numerical margins — "crop exactly 15mm from the top" — you generally need a desktop tool with numeric input fields.
Cropping on Mac With Preview
Preview on Mac can crop PDF pages through a slightly indirect method. Open the PDF, select the rectangular selection tool from the toolbar, draw a selection over the area you want to keep, then go to Tools → Rectangular Selection and use Tools → Crop (or Command+K). Preview applies the crop to the current page. Save using File → Export as PDF.
The limitation with Preview is that it crops one page at a time and the crop tool behavior varies slightly between macOS versions. For cropping a single page it works fine; for cropping all pages in a long document to the same dimensions, a dedicated tool is more efficient.
Extracting a Specific Region as an Image
If the goal is to extract a specific section of a PDF page — a chart, a diagram, a table — rather than crop the page itself, taking a screenshot and saving that region as an image is often more practical. On Mac, Command+Shift+4 lets you drag a selection and captures exactly what's on screen. On Windows, the Snipping Tool does the same. This is faster than cropping the PDF page and works regardless of any tool limitations.
The tradeoff is resolution — a screenshot captures what's on screen at screen resolution, typically 72-144 DPI depending on your display. If you need the extracted content at print quality, use a proper PDF crop and then convert that page to an image at 300 DPI rather than taking a screenshot.