When preparing a document to send to a printer, there are several specifications and elements to include in your layout. These specs help to insure that the printer will provide your final project as intended.
Trim marks, or crop marks, show the printer where to cut the paper. For a standard layout, such as a business card or poster, trim marks are small lines located in each corner of the document. One line shows the horizontal cut, and one shows the vertical cut. Since you don’t want these lines to actually show up on your printed piece, trim marks are placed outside of the final visible, or “live,” area.
When working in graphics software such as Illustrator, you can set your trim marks to be shown on screen and automatically placed in your final document export, such as a PDF. If you have downloaded templates from a printer, the trim marks will often already be included.
Trimmed Page Size
The trimmed page size is the final intended size of your pages, after being cut along the trim marks. This size is important to supply to the printer because it will determine what machines will be used to print your job, which will affect the final cost. When starting a project, the size you create your document at in a graphics program is the trimmed page size.
It is often necessary to have images and other design elements extend all the way to the edge of your printed page. If in your layout these elements only extended to the edge, and not beyond, you would risk a tiny bit of white space showing up on the edge of your paper if it was not cut exactly on the trim marks. For this reason, you have bleeds. Bleeds are images that extend beyond the live area of the page (and beyond the trim marks) to guarantee clean edges. Background colors are an example of a common use of a bleed.
The amount that your images need to extend beyond the trim marks is referred to as the bleed. Be sure to consult your printer at the start of a job to find out the required amount of bleed, which is often around one-eighth of an inch. In your graphics software, you can use guides to mark your bleed area, which do not need to show up in the final document that you deliver. Just make sure any image that needs to extend to the edge of the page actually extends to your bleed guides.
Margin or Safety
Just as images that should bleed should extend beyond the live area of your layout, images that you don’t want to risk getting clipped should stay within a margin, sometimes referred to as a “safety.” Again, consult your printer for these measurements. Just as with bleeds, you can set up guides to help stay within your margins.
David Bann. “The All New Print Production Handbook.” Watson-Guptill Publications. 2006.