Private Sub mergePdfButton_Click(ByVal sender As Object, ByVal e As EventArgs) Handles mergePdfButton.Click ' Create the merge result PDF document Dim mergeResultPdfDocument As 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 Dim outPdfFile As String = "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 Dim firstPdfDocumentToMerge As New Document(firstPdfFilePathTextBox.Text) ' Merge the first PDF document mergeResultPdfDocument.AppendDocument(firstPdfDocumentToMerge) ' Load the second PDF document to merge Dim secondPdfDocumentToMerge As New Document(secondPdfFilePathTextBox.Text) ' Merge the second PDF document mergeResultPdfDocument.AppendDocument(secondPdfDocumentToMerge) ' Save the merge result PDF document in a memory buffer Dim outPdfBuffer() As Byte = mergeResultPdfDocument.Save() ' Write the memory buffer in a PDF file System.IO.File.WriteAllBytes(outPdfFile, outPdfBuffer) Catch ex As Exception ' 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 End Try ' Open the created PDF document in default PDF viewer Try Process.Start(outPdfFile) Catch ex As Exception MessageBox.Show(String.Format("Cannot open created PDF file '{0}'. {1}", outPdfFile, ex.Message)) End Try End Sub