What is a Bleed?
Bleed refers to printed area that goes beyond the edge of the final page size before it is trimmed. In other words, bleed is the area to be trimmed off. It gives the printer some space to account for the paper shifting in the press. Artwork and background colors should extend into the bleed area to ensure that the final product will have no blank or unfinished edges once it is trimmed.
Standard bleed size in USA is a 1/8 inch on each side of the document (0.125 on the right, left, top and bottom).