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