Bleed is the image (ink) that prints beyond the trim edge of the page to ensure it extends to the edge of the page after trimming. As there is a degree of movement when printing on any press, you should always create 3mm bleed on all edges where bleed is needed.
Supplying your job without bleed may result in white lines when it is trimmed. The cutting process is not exact. There is in fact a 1-2mm tolerance. The idea of the bleed is that it accounts for this margin of error. This can be seen here:
In the above example, we can see that a flyer has gone to print without a bleed. The trimming process has gone a bit wrong (but within its tolerance) and the finished product is left with a nasty white line down the side. In the other image, we can see what happens when over-trimming occurs. The design went to print with no bleed and with text running all the way up to the side. Here, the trimming process actually trimmed too far and into the actual design. Both scenarios are far from ideal.
The solution is to add a bleed to your design. This gives a margin of error when trimming. The industry standard bleed size is 3mm, no matter the size of paper being printed. This is how it should look:
This piece of artwork has a 3mm boarder running around the outside of the main design (denoted by the white line). Importantly, nothing integral to the actual design (text, photos, patterns) falls within this section- just the background of the artwork.
How to apply Bleed
The concept of applying bleed is the same for all desktop publishing programmes. You need to extend the object box, whether picture or colour, out past the edge of your page. Then, when creating the PDF, you need to set your bleed margins to 3mm. InDesign, Publisher and Photoshop all allow you to adjust the ‘canvas size’ of your image.
When you start designing, make sure your canvas size incorporates a bleed. With Microsoft Word, PowerPoint or Photoshop you do not have the ability to add bleed when creating a PDF. You need to make your page/image size 6mm bigger at the start. You will then treat the extra 6mm (3mm all round) as bleed, which will be removed when the job is trimmed. For example, A4 is 210mm x 297mm. Your page with bleed will be 216mm x 303mm.
Example of adding 3mm bleed
Here we are using Photoshop. We are about to start designing an A6 flyer, the dimensions of which are 10.5cm x 14.8cm. However, I’d like to add on the 3mm boarder. That means I am actually adding on 6mm to the height and 6mm to the width (to account for the 3mm on both sides). Once the canvas is set up, I am able to drop down smart guides to show me exactly where my bleed finishes. I can then work safe and sound within this boundary.
Smart guides are available in all major design programs so have a Google if you need to know how.
So don’t forget, although bleeds are excruciatingly boring, they can stop your design from being ruined and can speed up the time period it takes for everything to arrive. Make sure you get exactly what you want by including bleeds on your designs.
We thought we’d put down a handy bleed table. Here it is:
Paper Size Finished Paper Size (cm) Paper Size with Bleed (cm)
Example of adding 3mm bleed – Illustrator