Brother MFC-3420C - Manual (Page 102)

4 - 26 USING THE WINDOWS ® XP-BASED BROTHER SMARTUI CONTROL CENTER
Select the number of Pages Per Sheet from the Scaling selections.
As an example to configure the section Copy button to copy two
pages to one you must select 2 in 1.
You must configure each of the copy buttons before they can be
used.
(From MFC-3220C)
(From MFC-3220C)