Bleed should be added to all print documents that have a block of color or image that goes right to the edge of the page.
What is bleed? Bleed in the commercial printing world is 1/8th of an inch (0.125 inch) of extra space outside the trim size of your document. In most programs, there is a setting when you first create your file where you can specify the bleed for that document.
Why do we need it? If there wasn’t bleed in your document for a block of color or image that goes right to the edge of the page, when we trim or fold the page there might be a fine white line showing. When we trim your job we usually have a stack of paper about 2-3 inches high. Our cutters slice down through the stack. Even though we put tons of pressure (literally) on the sheets to hold them in place, there is still the possibility the sheet may slip. If the sheet slips and there is no bleed, you may end up with a white line just at the edge of your page.
If your job die cuts, we might ask for a ¼ of an inch (0.25 inch) of bleed. In die cutting the process is not as precise as cutting and folding. A die can, in extreme cases (which are rare), shift an 1/8 of an inch. By asking for the ¼ inch bleed, we can avoid a white line from showing up. These cases are rare, but occasionally we will ask you to add the additional bleed, just to be safe.
When you send us open files, we can make this adjustment for you, provided there is enough image to cover the bleed. But if you supply us with PDF files, you will be responsible for making sure the bleed is correct. We can’t add bleed to a PDF file.
We want your files to look their best when they are done. So, if we seem to be adamant about bleed being on your files, it is because we know you won’t be happy if that white line shows up. So, bear with us, we want your printed pieces to look their best.