Auto-cropping reduces the visible area of a page leaving just enough for its contents. For example, if a page contained only a photograph and a caption with a large empty border, after auto-cropping the empty space would be trimmed away leaving just the image and its caption.

Cropping does not remove any information from the PDF, it just hides it from view.

  1. Choose Pages->Auto-Crop... 
  2. Choose a page range over which to apply the crop.
  3. Press OK.
  4. You can undo a crop by choosing Pages->Remove Crop...