What is bleed?

What is the safety zone?
To avoid being trimmed off, text and other important matter must stay within a "safety zone" that is is a minimum of .125" (3mm) away from the trim edge. Any design elements that extend beyond the safety zone risk being cut off in the process of trimming the paper to its finished size. For example, the safety zone for an 8.5" x 11" letterhead would be .125" smaller on each side, or 8.25" x 10.75".

bleed before and after illustration
Bleed Before and After Trimming 
The illustration on the left shows a document designed with bleed (finished size plus an extra .125" (3mm) on each side). Because minor variations can occur when cutting the paper to its finished size, to avoid being trimmed off, text and other important matter must stay .125" (3mm) away from the trim edge (the "safety zone").

The illustration on the right shows the printed piece after trimming. Note the last "e" in "Example" has been cut in half because it extended past the safety zone and into the trimming area. Some of the artwork has been cut off for the same reason. Any elements that extend past the safety zone risk being lost in the process of trimming the paper to its finished size.
How do I create bleed in my design?
To create bleed in your design, simply make sure the background color, graphic, or image you want it to bleed extends off the the final trim edge of the page by .125" (3mm).

If you are creating your file in an application such as Photoshop, you must make your document height and width dimensions .25" (6mm) larger than your final trim size. For example, if the finished size is 8.5" x 11" then make your document 8.75" x11.25". Position guides that are .125" from each edge. For design purposes, these guides will represent where the paper (and any of your design elements) will be cut.

Position any background color, graphic, or image that you want to bleed so they extended past your guides, all the way to the outside edge of the document. Remember, the extra .125" will be cut off after your piece is printed.