Bleed allows you to have colour run right to the edge of the page where you need it. On a printing press, the artwork is printed on a large sheet of paper and then cut down to size.
Why is adding a bleed necessary?
Small mechanical cutting variations can end up leaving a hairline white edge where there should be no white edge at all. This will happen if your image is not extended beyond the final cut size. Extending images 3mm beyond the final cut size guarantees that images truly will go all the way to the edge of the printed paper.
Build your artwork larger than the final size you need. For example, if you have designed a standard business card at 85mm x 55mm with an green background covering the whole area (like below), you will need to enlarge that green background. With our business cards we usually need 3mm bleed on each edge. So your background should stretch to 91mm x 61mm total size. Contact us for help. firstname.lastname@example.org