The PDF/X standards are becoming increasingly popular methods of delivery of graphic arts content from one company or site to another. A file prepared in accordance with the standards is likely to process through a prepress workflow with no errors and a more predictable result than a general PDF file. It's worth remembering, however, that part of the reason for the predictability is that the PDF/X standards are not just file formats - they also specify correct rendering behavior of the files in the RIPs driving proofing printers, image setters and CTP devices.
The Global Graphics PDF/X overprint control strip is supplied as an EPS file that can be placed outside the trim or bleed area of a job in a design application. When the job is later converted to one of the PDF/X conformance levels and then proofed or printed, the strip will show whether or not the rendering process in that proofing or prepress system has been configured in conformance to the PDF/X standards. It may also be placed on a press sheet by an imposition application.