// Create a new workbook Workbook workbook = new Workbook(); workbook.open(this.getResourceStream("xlsx/PageSetup Demo.xlsx")); IWorksheet worksheet = workbook.getWorksheets().get(0); //Set A4 paper size worksheet.getPageSetup().setPaperSize(PaperSize.A4); // Save to an excel file workbook.save("ConfigPaperSize.xlsx");