botMargin (USHORT)
The value in this field defines the bottom unprintable area for this input. The bottom margin is defined as that area below the last printable line written in the marking direction. The units for this value are specified by lengthUnits in the PRTDEVCHAR data structure. A value of hex 'FFFF' indicates that the printer does not have, nor can it determine, this value.
Note: This value specifies the limitation of the printing mechanism and also indicates that particular page interpreters may place additional limitations on the margins.