[CentOS] Package pxljr-1.1-1.i386.rpm (from kde.repo) is not signed

I'm trying to install the driver for an HP Colour Laserjet 3500 in
CentOS 5. I've installed the kde.repo (with appropriate priorities set
up), but when I try yum install pxljr-1.1-1.i386.rpm, I get the above
message that 'the package is not signed'. I've previously tried running
yum localinstall on the downloaded package with the same result. How do
I resolve this please?

Andy