To install cups: pacman -Syu cups
Unfortunately, the archlinux wiki page for cups is not detailed enough, and does not include the above command.
When you installed libcups, it was only the library, not the software that utilizes the library. Also, the fact that lpr is a standard command in bash, does not mean that it comes with bash. The other computers you have, already have printing installed, so bash can find the commands. In Arch, users need to add a package with those commands, and cups is that package.