When designing any material going to print, you have to decide if you need a bleed or not. A bleed will keep your design for brochure, postcard, or poster printing from having unprinted edges.
What is Bleed?
The bleed is the area of printing that extends past the edges of your document. If you want color to extend to the very edges of your brochure or poster printing piece, you will need to create a bleed. Printing color past the edges of your piece allows for slight shifts of the printing plates and the cutting machines. If there were no bleed, then the slight shifts would result in slivers of white, unprinted paper showing on the edges.
When a printer offers full bleed, it means they can give you a printed piece that has color extending from one edge to the other. Some smaller printers do not offer full bleed; they have to leave a white or colored border surrounding your design.
What Needs to Bleed
If you want color to extend from one side to the other of your business card or poster printing design, then you need to keep in mind what graphics are at the edges. You will want to keep text inside the document with a border of color around it. If you use large graphic text, you can extend the text past the edges into the bleed; just make sure the letters are large enough that it will not look distorted if slivers are cut off the edges. If you are using a photograph as the background of your piece, then keep in mind that the edges will get cut off.
The most common amount of bleed in the United States is 1/8 of an inch (0.125), but you will need to ask your printer to be sure how much they need. If you are designing something that will be die cut, then you will probably need a 1/4 inch bleed to allow for extra shifts of the die cutters.
Creating a Bleed
It is the designer's responsibility to create the bleed. If a file is sent to a printer without a bleed built in, the printer will either charge extra to create one for you, or the printer will send the file back to you. You can create a bleed as you go or wait until pre-press preparations. Some designers like to wait until the end because they want to design a piece knowing how the final product will look; creating a bleed as you go can skew the proportions.
If you need a 1/8 inch bleed all around, you will need to add 1/4 inch all the way around the document. Then extend the colors to the edge of the bleed. Leave rulers where your document ends and the bleed begins. The actual edges of your document are called the trim line. Most printers should provide a template to place over your design to make sure your trim and bleed lines are where they need to be.