Adobe's official crop guide describes a Set Page Boxes dialog used to adjust a page's CropBox margin values directly. Crop pages in PDFs using Acrobat on desktop | Adobe Acrobat
Crop PDF starts each margin field at 36, which is 36 points, or half an inch, before any value is changed.
Crop PDFCrop PDF Margins in Points
Enter margin values in the top, right, bottom, and left fields using points.
Crop PDF rejects a margin value entered above 1000, since MAX_CROP_MARGIN caps each side at 1000 units.
Multiply your desired inch measurement by exactly 72 points per inch to get the correct point value for that margin.
Checking Crop Results
Download the processed PDF and compare the new page dimensions against your target size.
Adjust the margin values and reprocess the file if the crop depth differs from your expectation.
Continue with Margins do not fit page or Rotated pages.
Frequently Asked Questions about Crop PDF Margins in Points
How do I convert inches to points for cropping?
Multiply the inch value by 72 to calculate the point equivalent.
Where do I enter the margin values?
Type the point values into the top, right, bottom, and left input fields.
How do I fix a margin that is too large?
Reduce the numeric value in the specific margin field and reprocess the document.
Where do I find the default margin setting?
Check the initial values in the four margin input boxes before making changes.