CUPS PDF files (application/vnd.cups-pdf) are device-dependent
PDF/A files that contain a job ticket information. These files
are typically produced by the CUPS pdftopdf
filter
which handles job ticket generation, imposition, page labeling,
scaling, and other formatting options requested by the user. CUPS
PDF files are intended for direct consumption by a PDF-capable
printer, PDF RIP, or the pdftops
filter.
More information will be posted here as the PDF workflow filters are added to CUPS.