问无法使用VBSCRIPT从pdf中检索字段

EN

FileNm = "IMM0008ENU_2D.pdf" 'File location
Set gApp = CreateObject("AcroExch.app")
Set avDoc = CreateObject("AcroExch.AVDoc")
   If avDoc.Open(FileNm, "") Then
   Set PDFForm = CreateObject("AFormAut.App") 
   set x=PDFForm.Fields
   wscript.echo "total fields:",x.count
      For Each myField In x
      Wscript.echo myField.Name
      Next
   End If
avDoc.Close (True) 
Set gApp = Nothing
Set avDoc = Nothing
Set PDFForm = Nothing