The print service provider should give you some guidelines for submitting job files. Some prefer PDF files, while some would rather have application files such as QuarkXPress, InDesign, or Illustrator. Usually, you’ll be asked to provide multipage documents in reader’s spreads, which is how you normally build such documents: page two facing page three, and so on. If you’re asked to provide printer’s spreads—imposed for plating—you should be suspicious that the printer doesn’t have dedicated software to perform imposition. This may be a sign that the printer lacks other important capabilities.