To understand why you need trim/crop marks - it is helpful to first understand what these are, in a commercial printing context. What are Trim or Crop marks? They are marks that are on each corner of the page that indicate where the paper needs to be trimmed. When we print almost any print job, we actually print on a larger sheet of paper or stock.During the pre-press stage of production, we will undertake a process called 'imposition'. This is where we try and fit as many of the same artwork on a single sheet of paper. For digital technology, the maximum sheet size is an SRA3, which is slightly larger than an A3. This process is how we can produce printing that is cost effective, high quality and reduces waste.When the sheet is printed, we then trim it to size on our guillotines or trimming machines.This is where trim (or crop) marks are essential.We use these marks to accurately trim to size, on each edge.The name changes based on the software you use. In Adobe InDesign, they are called Crop marks. In Adobe Illustrator - Trim marks. A Pdf With Trim Marks highlighted (bleed extends beyond these marks)When exporting for print, the only options you need to select in the Printers marks are are: Trim/Crop and Document Bleed settings (ensure your document has 3mm bleed). Unless we advise differently (i.e. for some offset, packaging and other specialty printing), you don't need to select registration, colour bars or page information.So - if you've exported it correctly, the image on this page is how your PDF should look with trim/crop marks and bleed. I have highlighted the trim marks. Note how the artwork extends beyond the trim marks. This is the bleed.
