xpdf-japanese is unusable without fonts-ja (it shows latin-1 characters without it)
I would guess that other xpdf-variants have the same problem, ie. they need to
depend on the necessary font packages to be usable.
with xpdf-2.02-4, i have merged sub packages to main package.
Adding requires fonts-ja will not make sense because the correct font rpms are
installed by new installation.