Bleeds are important for any print file which the artwork extends to the edge of the printed piece. A bleed is an extension of the artwork past the finished size of the printed piece that will be cut off. A 1/8 bleed is recommended on all artwork where the art extends to the edge of the printed piece.
The reason bleeds are needed is that artwork is printed on large sheets and then cut down to size. This is needed to increase efficiencies and reduce cost and because printers will not print to the edge of the paper. When printing and cutting there can be slight misalignments and if a bleed is not included the printed piece can have white space on the border instead of the artwork extending to the edge.
The best way to add a bleed is to ensure your artwork is setup correctly when beginning your design. Most designers should be familiar with how to do this, or give us a call and we can walk you through the process. We sometimes can add bleeds to artwork after they have been created but it depends on how the artwork is setup and the format the artwork is sent as. It is always preferable to receive the artwork with bleeds included in the original design as any manipulations can effect the artwork.
Bleeds are important to ensure that artwork is printed and cut correctly to get the best quality from your printing.