<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <html> <head> </head> <body> These are the low level objects that make up a PDF document. <br/><br/> See the <A href="http://partners.adobe.com/asn/developer/acrosdk/docs/filefmtspecs/PDFReference.pdf">PDF Reference 1.4</A>. </body> </html>