The printing guide instructs users to enable usblp in their kernels when using USB printers. CUPS 1.4 is incompatible with this option, as explained in Bug #285166.
It would be helpful if the printing guide explained this, say by changing
"To enable USB printing, you need USB support and USB printer support..."
"If using a CUPS version less than 1.4, to enable USB printing, you need USB support and USB printer support... For versions 1.4 and greater, make sure to disable this option, as it interferes with CUPS."
We don't document ~arch packages, only the stable tree. Please reopen once cups-1.4.x is marked stable.