Im having an issue on our print server where im unable to change 'paper available' to A4 from letter. This is causing issue with users using the print server since applications like MS word will keep defaulting to letter.
A4 has been set in General > preferences as well as Advanced > Printing Defaults. Any printer that uses this driver are all set to letter under 'paper available'.
I am not sure if this will help, but I found a setting from the KB called Allow Paper Substitution for Prints. The steps on this setting are located HERE.
Too late for OP, but for anyone else struggling with this...
Check the Windows "System Locale".
After changing it from "English (United States)" to "English (New Zealand)" this issue was resolved for me.