The popt tarball includes a popt.ps that should be included in the popt rpm
as a %doc. You might also consider including the README and CHANGES from
the popt tarball as %doc's for the popt package.
Distributing an aging popt.ps document doesn't make much sense.
These days, popt is distributed as a sub-package of rpm, so the README and
CHANGES file are not very useful either.