Xerox Docuprint driver

I asked before but could not get back because of PC problems. MY Xerox DocuPrint C20 poses a real problem when I try to change between A3 and A4. I am just using A4 at the moment. If I set it to A3 on the printer the print comes out in odd shapes. Icannot do it from the computer neither. The driver does not allow for changing, or cleaning, cartridges. I have to pull the plug out and change to cartridge. Xerox on line line has a list of docuprint C20s and I canot figure which one is correct to download.
Donald