Select the Watermark size.
The following shows where you can select this function.
Type 1
[Watermark Size] is displayed under [General 2] in the [Feature Sets:] list on [Printer Features] in the print dialog box.
Types 2 and 3
[Watermark Size] is displayed under [General 3] in the [Feature Sets:] list on [Printer Features] in the print dialog box.