Page boxes

The exact size of a PDF page is not as straightforward as it seems because there might be up to five different descriptions in a PDF that relates to its size. These are called page boxes.

• Media Box: this is the largest page box in a PDF. The other page boxes can be equal to the Media Box but they should not be bigger. In prepress use, pages are defined slightly oversized so that the bleed, the crop marks, information panels and other useful information are visible as well. This means that PDF documents used in graphic arts usually have a Media Box, which is bigger than the trimmed page size.
• Crop Box: this is the region to which the page contents are to be clipped. Adobe Acrobat uses this size for screen display and printing. For prepress use, the Crop Box is irrelevant.
• Bleed Box: this box determines the region to which the page contents needs to be clipped when output in a production environment. Usually the Bleed Box is 3 to 5 millimeters bigger than the Trim Box. Most prepress systems allow you to define the amount of bleed and ignore the Bleed Box.
• Trim Box: this defines the intended dimensions of the finished page. Unlike the Crop Box, the Trim Box is very important because it defines the actual page size. Most imposition programs and workflows use the Trim Box as the base for positioning pages on a press sheet or labels and packaging on a step and repeat.
• Art Box: the Art Box can define a region within a page that is of special interest. It is rarely used by applications.