Hello,
the manual for pdfTeX 1.40.15 writes in table 2, that the default value
for \pdfminorversion is 4. However the description for \pdfminorversion
says it's 5.
I think, the latter is wrong, because
pdftex --ini '\showthe\pdfminorversion\end'
reports 4.
Yours sincerely
Heiko
