Why Is Bleed Important?
In commercial 4 color printing, all final jobs are cut in stacks. The accuracy
of cutting in stacks is never perfect. Sometimes, the pressure on the stack from
the cutting blade will cause a slight shift on the paper, losing the precision
of the intended cut. This is why bleed is necessary to compensate for the
shifting.
If bleed is not provided on a document, the final result of a trimmed job may
possibly result in a slight white border around the edge. The example below will
illustrate why bleed is important.