'This code demonstrates merging multiple PDFs
On Error GoTo error
Dim pdfXpress1 As  New PdfXpress
pdfXpress1.Initialize
pdfxpress1.RaiseExceptions = True
Dim docpageList As New PageList
Dim docpageRange As New PageRange
docpageList.Add docpageRange
Dim insertOpts As InsertPageOptions
insertOpts.PageList = docpageList
docpageRange.StartPageNumber = 0
docpageRange.pageCount = 1
Dim numDoc As Integer
 numDoc = 4
Dim so As New SaveOptions
so.FileName = "C:\merged.pdf"
Dim doc_merge As New PdfDocument
doc_merge. SetParentControl pdfXpress1
doc_merge.NewDocument
Dim a As Integer
For a = 0 To pageCount - 1
         Dim doc_new As New PdfDocument
         doc_new.SetParentControl pdfxpress1
         doc_new. OpenDocument  "C:\split" + CStr(a) + ".pdf", ""
         insertOpts.SourceDocument = doc_new
         insertOpts.InsertAtPageNumber = a
          doc_new.InsertPages insertOpts
Next a         
doc_new.SaveDocument so
.
.
.
GoTo finish
error:
MsgBox Err.Description
finish:

Set document = Nothing
pdfxpress1.Terminate
Set pdfxpress1= Nothing