The setPaperSize(short) method in HSSFPrintSetup does not currently support A3 papersize. (Supports A4,A5,Letter,Legal, Executive and a few Envelope sizes only). For large reports, A3 seems important. Would it be possible to add this also ?
Any chance you could upload two very simple otherwise identical files, one set to A4, and one set to A3? That'll be useful for double checking the settings needed in the file for A3, as well as being the basis for the unit tests for the feature once added.
I tried to create A3 size excel files. With a missing support for A3, i read an existing file and found the (short) vaule 8. Using sheet.getPrintSetup().setPaperSize((short)8); seems to be a workaround to create A3 excel files.
I've added constants for a number of missing sizes, including A3, in r929064.