How can I add page size A0 to Microsoft XPS Document Writer?

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C#

MS-Excel

PDF

Hello,
in my c#-code is written:

excelWorkbook.ExportAsFixedFormat(Microsoft.Office.Interop.Excel.XlFixedFormatType.xlTypePDF,
Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location) +
"\\" + output)

It makes a pdf-file in A4, not in A0. I had to add page size A0 to Microsoft XPS Document Writer manually, but how does it work in c#?

A4 means 210 × 297 mm
A0 means 841 × 1189 mm