CreateObject("pdfforge.pdf.pdf") + VBA

I want to sign pdf with PDFCreator and macro VBA, I am using the script SignPDF but it crash in the line Set pdf = CreateObject("pdfforge.pdf.pdf")

"erreur d'execution(80070002)  File or assembly name pdfforge, or one of its dependencies was not found"

Sub MAIN()
  Dim pdf
  Set pdf = CreateObject("pdfforge.pdf.pdf")
  Set enc = CreateObject("pdfforge.pdf.PDFEncryptor")
  pdf.SignPDFFile "c:\\Doc1.pdf", "", "c:\\output.pdf", "c:\\certif.pfx", "mypassword", "The signature reason", "The signature contact", "The signature location", True, 1, 10, 10, 50, 50, False, (enc)
  Set pdf = Nothing
  Set enc = Nothing
End Sub