\pdfmajorversion

[Akira Kakuto]

Dear Joseph,

> As it is, pdfTeX already allows 1.9, which I do not beleive
> exists. Tracking every PDF version seems challenging.

Sorry, I was wrong. [x]dvipdfmx allows
PDF_VERSION_MIN <= pdf_version <= PDF_VERSION_MAX,
where pdf_version = 10 * pdf_version_major + pdf_version_minor,
PDF_VERSION_MIN = 13, and PDF_VERSION_MAX = 20.
So 1.9 is allowed also in [x]dvipdfmx.

Thanks,
Akira