public static void Run() { //Source directory string sourceDir = RunExamples.Get_SourceDirectory(); //Output directory string outputDir = RunExamples.Get_OutputDirectory(); //Certificate file and its password string certFileName = sourceDir + "AsposeDemo.pfx"; string password = "******"; //Load the workbook which is already digitally signed to add new digital signature Aspose.Cells.Workbook workbook = new Aspose.Cells.Workbook(sourceDir + "sampleDigitallySignedByCells.xlsx"); //Create the digital signature collection Aspose.Cells.DigitalSignatures.DigitalSignatureCollection dsCollection = new Aspose.Cells.DigitalSignatures.DigitalSignatureCollection(); //Create new certificate System.Security.Cryptography.X509Certificates.X509Certificate2 certificate = new System.Security.Cryptography.X509Certificates.X509Certificate2(certFileName, password); //Create new digital signature and add it in digital signature collection Aspose.Cells.DigitalSignatures.DigitalSignature signature = new Aspose.Cells.DigitalSignatures.DigitalSignature(certificate, "Aspose.Cells added new digital signature in existing digitally signed workbook.", DateTime.Now); dsCollection.Add(signature); //Add digital signature collection inside the workbook workbook.AddDigitalSignature(dsCollection); //Save the workbook and dispose it. workbook.Save(outputDir + "outputDigitallySignedByCells.xlsx"); workbook.Dispose(); Console.WriteLine("AddDigitalSignatureToAnAlreadySignedExcelFile executed successfully.\r\n"); }