Dim PDF1 As String = "C:\Test\pdf1.pdf"
        Dim PDF2 As String = "C:\Test\pdf2.pdf"
        Dim combinedPDF As String = "C:\Test\combinedpdf.pdf"
        Dim outputDocument As PdfDocument = Nw PdfDocument()

        If File.Exists(PDF1) Then
            Dim inputDocument As PdfDocument = PdfReader.Open(PDF1, PdfDocumentOpenMode.Import)

            Dim PDFPageCount As Integer = inputDocument.PageCount
            Dim count As Integer = 0
            While count < PDFPageCount
                Dim page As PdfPage = inputDocument.Pages(count)
                outputDocument.AddPage(page)
                count += 1
            End While
        End If

        If File.Exists(PDF2) Then
            Dim inputDocument As PdfDocument = PdfReader.Open(PDF2, PdfDocumentOpenMode.Import)

            Dim PDFPageCount As Integer = inputDocument.PageCount
            Dim count As Integer = 0
            While count < PDFPageCount
                Dim page As PdfPage = inputDocument.Pages(count)
                outputDocument.AddPage(page)
                count += 1
            End While
        End If

        outputDocument.Save(combinedPDF)

        outputDocument.Close()
        outputDocument.Dispose()
        outputDocument = Nothing

        Process.Start(combinedPDF)