If you send us a finished DIN A4 PDF, the page is usually exactly 210 × 297 mm.
For professional printing, however, we need an additional 3 mm margin all around, known as the bleed. This means that 210 × 297 mm becomes 216 × 303 mm.

To create this trim margin, we need to scale up your document—that is, slightly enlarge the image so that it fits within the larger area.
Here’s what happens:

• Anything that is right up against the margin in the original PDF is pushed outward as a result of the enlargement.

• This outer area consists of the 3-mm trim margin, which will be cut off later during the cutting process.

• Content that was previously just inside the margin may then partially fall within the trim margin and could be trimmed off or missing entirely in the final print.

To prevent that from happening, there’s a simple rule:

• Important content (text, logos, key lines, pictograms) should be at least 6 mm from the edge in the original DIN A4 PDF.

• Since we need to add another 3 mm for the bleed, these 6 mm will result in a total distance of 9 mm from the outer edge in the final product.

• This way, we ensure that when we enlarge the image for cropping and later trim it, nothing important is pulled into the crop margin and cut off.

Only elements that are intentionally meant to be “borderless”—such as full-page backgrounds or images—may extend all the way to the edge and later fall within the bleed area.
Everything else should be placed with a safety margin of at least 6 mm in the original document to ensure that it remains safely within the visible area even after the bleed is added.