The BleedBox is one of the five PDF boxes. It describes the part of the PDF, including the content and the bleeding. In printing a bleed of 1 to 3 mm is usually required. A PDF file with an A4 page for printing so usually has a Trimbox of 210×297 mm, the trimmed page format. The BleedBox has with 3mm bleed around the page the size of 216x303mm.
The CropBox is the second largest box of a PDF file. It describes the part of a PDF file which is to be output to a printer or screen. It is often the same as the Mediabox.