public void MergeJbig2Files(System.IO.Stream firstStream, System.IO.Stream secondStream)
{
    // open the first JBIG2 file
    using (Vintasoft.Imaging.Codecs.ImageFiles.Jbig2.Jbig2File firstJbig2File = 
        new Vintasoft.Imaging.Codecs.ImageFiles.Jbig2.Jbig2File(firstStream))
    {
        // open the second JBIG2 file
        using (Vintasoft.Imaging.Codecs.ImageFiles.Jbig2.Jbig2File secondJbig2File = 
            new Vintasoft.Imaging.Codecs.ImageFiles.Jbig2.Jbig2File(secondStream))
        {
            // for each page in the second JBIG2 file
            for (int i = 0; i < secondJbig2File.Pages.Count; i++)
            {
                // add page of the second JBIG2 file to the first JBIG2 file
                firstJbig2File.Pages.Add(secondJbig2File.Pages[i]);
            }
            // save changes to the first TIFF file
            firstJbig2File.SaveChanges();
        }
    }
}

Public Sub MergeJbig2Files(firstStream As System.IO.Stream, secondStream As System.IO.Stream)
    ' open the first JBIG2 file
    Using firstJbig2File As New Vintasoft.Imaging.Codecs.ImageFiles.Jbig2.Jbig2File(firstStream)
        ' open the second JBIG2 file
        Using secondJbig2File As New Vintasoft.Imaging.Codecs.ImageFiles.Jbig2.Jbig2File(secondStream)
            ' for each page in the second JBIG2 file
            For i As Integer = 0 To secondJbig2File.Pages.Count - 1
                ' add page of the second JBIG2 file to the first JBIG2 file
                firstJbig2File.Pages.Add(secondJbig2File.Pages(i))
            Next
            ' save changes to the first TIFF file
            firstJbig2File.SaveChanges()
        End Using
    End Using
End Sub