Preflighting for PDF/X-Compliance with Acrobat
http://www.planetpdf.com/creative/article.asp?ContentID=6114

PlanetPDF
2001

Abstract:

PDF/X (PDF Exchange) is a subset of Adobe PDF that eliminates many of the color, font, and trapping variables that lead to printing problems. You can verify that a PDF document is PDF/X-compliant in Adobe Acrobat 6.0 Professional before submitting the document to a service provider, and then embed the verification results in the file.