\pdfmajorversion

[Karl Berry]

    > I think that non-existing version numbers should not be allowed.

I don't have a solution for disallowing 1.9, but to avoid passing
through obvious errors like "PDF 9.4" or "0.0", maybe there should a
maximum version number defined at runtime in yet another primitive, like
\pdfmaxversion=200 (choose whatever arithmetic algorithm suits). Thus it
would be built into the formats and if a new PDF version is released, it
would not require new binaries.

I'm not sure if it's worth it, but that's what comes to mind.
Wdy(all)t? -k