Our artwork check looks for the things most likely to cause print or finishing issues: bleed, dielines, colour mode, image resolution, fonts, barcodes, white ink, foil masks and copy too close to the cut line.
If something looks risky, we flag it before proofing so the fix happens while it is still cheap and simple. You can check bleed and the cut line yourself first with the dieline generator and its bleed calculator. To see how RGB colours shift in CMYK before you send files, use our RGB to CMYK converter.