If the file has either an image or color that is to be printed to the edge, with no white border, this is a bleed and the file must be specifically formatted to accommodate the bleed. If you receive a file that has a bleed, you must examine it to determine if it is formatted properly. The importance of proper formatting is that nothing is absolutely precise when printing; sheets shift both in the printer and in the cutter and if the image ends right at the edge, there will be white showing on a good portion of the sheets. The added bleed ensures that even with some shifting, there will always be an image at the edge.
Picture 1 has No Bleed. Notice how the image ends right at the final trim dimensions (crop marks). This file will not print correctly.
Picture 2 is incorrectly formatted for a bleed. Notice how, despite the double crop marks showing, the picture still ends at the final trim dimensions (inside crop marks). This file, like Picture 1, will not print correctly.
Image 3 shows a file that is correctly formatted for a bleed. Notice how the image extends beyond the final trim dimensions (inside crop marks) by .125″ on each side. This file will print correctly.
