Donald upgraded his MacBook Pro to OS X Mavericks, but now he can't print. He has the printer connected to a PC, and is using Printer Sharing in Windows to print from the Mac. Leo says that Donald will have to delete and then re-add his printer.
Leo also says that there's a utility called CUPS, which can work if his printer is too old to be supported. Apple has a technote here that says whether or not he can use the generic PCL driver. There's also GIMP Printer.