In the design and prepress process, the designer is required to extend all visual elements that are intended to reach the final edge of the product by a standard measurement (typically a minimum of 3 to 5 millimeters) past the trim line. This safety margin is crucial due to unavoidable inaccuracies in cutting machines, such as slight vibrations or minor misalignment (register error) during the printing process.
If the Bleed is not included in the file, even the smallest deviation in the cut will result in an unacceptable border appearing along the edges of the printed piece. Therefore, Bleed must be correctly calculated in graphic design software and accurately applied when outputting final print files (such as PDF/X format) to ensure a flawless visual result.
Bleed is defined as an area, and its dimensions are added to the length and width of the main file. Cutting lines (trim marks) are always defined within the bleed area to cut this excess portion. Consequently, after trimming, the original and actual dimensions created by the designer are restored.