Comment 3 for bug 650454

su -c "rpm -ev --nodeps libsane-hpaio" will remove the previous libsane-hpaio package if any. If this package is not already installed then you can skip this step.

Please continue with the remaining installation steps.

I suggest you to install auto installation for Fedora. this will do all the steps mentioned in the link except disable SELinux.
Once you have completed the auto installation by download it from http://hplipopensource.com/hplip-web/install.html, please disable the SELinux mention in Step 8A in http://hplipopensource.com/hplip-web/install/manual/distros/fedora_core.html

Thanks,
Naga Samrat Chowdary, Narla