We've tried the link you suggested - and it didn't work.
We downloaded the installation program, and then executed it. We had three options, and chose the one to upgrade. The message told us that everything is completely up to date. But we still couldn't print.
So we then uninstalled the printer and using the installation program, installed it from scratch. This seemed to go OK.
It asked to be connected via USB cable. Even though the printer is physically connected to the computer and switched on, the message came up that the printer is not detected.
I don't know if this is relevant, but the printer cable linking the two is about 7 metres long, as they're on different desks in our study. This hasn't been a problem up to now. All problems started with upgrading from Windows 8 to 8.1.
We'd obviously downloaded the correct driver as suggested, but then had a second problem.
We had the printer connected via a USB hub. When we put the cable directly into the computer, rather than via the hub, the printer worked! We don't understand why it worked through hub before though, but for now will leave it as it is.