Checks whether trapnet information in a PDF is compliant with either PDF/X-1 or PDF/X-3 standards.
In printing, even the slightest misregistration of the plates can cause gaps or color shifts between colored objects to appear. Trapping is a technique that compensates for misregistration by expanding adjacent colored objects so that they overlap. Trapping can be performed by the source application, in the PDF, by dedicated trapping tools, or during the RIP-process.
If the traps in a document were added before the PDF document was created, they are included in the PDF file as trap networks. A page may have more than one trap network, e.g. one for each intended output device, but all the different trap networks are stored in the same trap network, also called trapnet annotation. When printed, the trapnet annotation provides all the required trapping information for the page.