private void mergePdfButton_Click(object sender, EventArgs e) { // Create the merge result PDF document Document mergeResultPdfDocument = new Document(); // Automatically close the merged documents when the document resulted after merge is closed mergeResultPdfDocument.AutoCloseAppendedDocs = true; // Set license key received after purchase to use the converter in licensed mode // Leave it not set to use the converter in demo mode mergeResultPdfDocument.LicenseKey = "fvDh8eDx4fHg4P/h8eLg/+Dj/+jo6Og="; Cursor = Cursors.WaitCursor; string outPdfFile = @"DemoAppFiles\Output\PDF_Editor\Merge_PDF.pdf"; try { // The documents to merge must remain opened until the PDF document resulted after merge is saved // The merged documents can be automatically closed when the document resulted after merge is closed // if the AutoCloseAppendedDocs property of the PDF document resulted after merge is set on true like // in this demo applcation // Load the first PDF document to merge Document firstPdfDocumentToMerge = new Document(firstPdfFilePathTextBox.Text); // Merge the first PDF document mergeResultPdfDocument.AppendDocument(firstPdfDocumentToMerge); // Load the second PDF document to merge Document secondPdfDocumentToMerge = new Document(secondPdfFilePathTextBox.Text); // Merge the second PDF document mergeResultPdfDocument.AppendDocument(secondPdfDocumentToMerge); // Save the merge result PDF document in a memory buffer byte[] outPdfBuffer = mergeResultPdfDocument.Save(); // Write the memory buffer in a PDF file System.IO.File.WriteAllBytes(outPdfFile, outPdfBuffer); } catch (Exception ex) { // The PDF creation failed MessageBox.Show(String.Format("Create PDF Document Error. {0}", ex.Message)); return; } finally { // Close the PDF document resulted after merge // When the AutoCloseAppendedDocs property is true the merged PDF documents will also be closed mergeResultPdfDocument.Close(); Cursor = Cursors.Arrow; } // Open the created PDF document in default PDF viewer try { System.Diagnostics.Process.Start(outPdfFile); } catch (Exception ex) { MessageBox.Show(String.Format("Cannot open created PDF file '{0}'. {1}", outPdfFile, ex.Message)); } }