Just for accuracy's sake: It wasn't created with Quark, which is page layout software. Quartz, on the other hand, is part of the native Mac OS X display software. It's also part of what lets the Mac write PDF files from any application. So, from what I read, the fact that the creator is listed as "Quartz PDFContext" probably means the scan was opened in some Mac program from which it was "printed" to PDF, or opened in the Mac's native graphics viewer (Preview) and exported as PDF.
Note that Preview has a "reduce file size" Quartz filter option. Some argue that its operation would account for many of the "anomalies" in the birth certificate.