// This code demonstrates how to merge multiple PDFs into one PDF 
Accusoft.PdfXpressSdk.PdfXpress  pdfXpress1 = null;
Document doc_merge = null;
InsertPagesOptions io = null;
Accusoft.PdfXpressSdk.SaveOptions so = null;
Document doc_new = null;
try
{
     pdfXpress1 = new PdfXpress();               
     pdfXpress1.Initialize();
     doc_merge = new Document(pdfXpress1);
     io = new InsertPagesOptions();
     PageList pageList = new PageList();
     PageRange pageRange = new PageRange();
     pageRange.StartPageNumber = 0;
     pageList.Add(pageRange);
     io.PageList = pageList;
     int numDocs = 4;
     so = new SaveOptions();
     so.Filename = "c:\\merged.pdf";
     OpenOptions oo = new OpenOptions();
     for (int a = 0; a < numDocs; a++)
    {
        io.InsertAtPageNumber = a;
        oo.Filename = "C:\\split" + a + ".pdf";
        doc_new = new Document(pdfXpress1,oo);
        io.SourceDocument = doc_new; 
        pageRange.PageCount = doc_new. PageCount;
        doc_merge.InsertPages(io);
    }
        doc_merge.Save(so);
}
catch (System.Exception ex)
{
}
finally
{
        if ( null != doc_new) doc_new.Dispose( );
        if ( null != so) so.Dispose( );
        if ( null != io) io.Dispose( );
        if ( null != doc_merge) doc_merge.Dispose( );
        if ( null != pdfXpress1) pdfXpress1.Dispose( );
}