What is Bleed in Printing?
Bleed occurs any time the area of an image extends beyond the trim edge of a sheet. That is to say, the image will extend all the way to the edge of your final printed page instead of including an outer margin that is left with no printed material. This can be true of all or just part of the page.
Does your document require bleed?
Whenever an image or object touches an edge of the page it is necessary to extend that object slightly beyond the edge. If nothing comes close to touching any edge then your document doesn’t require bleed.
Why is understanding bleed important?
Small amounts of paper movement during production or minor inconsistencies in design can result in unintended white space appearing at the edge of the page on your finished product. By extending images beyond the trim edge, you are assured that the image will end at the edge after the final trim.