Currently, up2date will only download/installed already installed packages. Via some means of adding packages which have not already been installed. This could be done via editing the rhn.redhat.com website or (preferrably) via up2date. Rational: When a system is first installed, many (but usually not all) packages are installed. After apply maintenance via up2date, a number of packages are updated. After some time passes, a new package is needed. Howeer, updated packages are installed so you cannot go back to the original cdroms to install the packages because or other dependencies. This can be especially true for an upgraded system.
Seems the current version has the capabilities