A version of pdftex as supplied is 0.13d.  This is a very old version
and is known to be affected by numerous bugs which are fixed in current
stuff (the latest release of "TeX Live" includes 0.14h).  To many
examples to list here but scan comp.text.tex newsgroup for a short
while and you will likely have a collection.

In general TeX installation is too much behind of current releases
and it shows.  TeX engine does not really change but various packages,
macros and auxiliary program do and some quite fast.  Right now you
can often encounter in comp.text.tex, in a response to trouble reports:
"Ah, Red Hat!  Get yourself something not broken instead."  One cannot
claim that this attitude is without a merit even if 'pdf...' program
family is the most blatant supporting example.