In printing, the term "bleed" refers to an area of a printed document that extends beyond the actual final size of the document. The bleed area is required during printing to ensure that the document is cut exactly to the edge after printing without leaving white margins or unprinted edges.
The bleed is necessary because when printing on large sheets, several documents are printed next to each other on one sheet. After printing, these sheets are then cut into individual documents. To ensure that the document is cut exactly to the edge, the print must be printed with a certain "allowance" on all sides. This allowance is usually around 3-5 mm on each side of the document.
Therefore, all elements that are to extend to the edge of the document (e.g. background colours or images) should extend into the bleed area to ensure that no unprinted edges are left behind. Before printing, the document must then be cut to the final size and the bleed area removed.
