// For complete examples and data files, please go to https://github.com/aspose-cells/Aspose.Cells-for-.NET
// The path to the documents directory.
string dataDir = RunExamples.GetDataDir(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

// Instantiating a Workbook object
Workbook workbook = new Workbook();

// Accessing the first worksheet in the Excel file
Worksheet worksheet = workbook.Worksheets[0];

// Setting the paper size to A4
worksheet.PageSetup.PaperSize = PaperSizeType.PaperA4;

// Save the Workbook.
workbook.Save(dataDir + "ManagePaperSize_out.xls");