If you are running this code on messages as they arrive using a rule, why are you then looking at all the items in inbox? It is the item that arrives that is of interest. So assuming that your file path is correct the following is all you require.

Public Sub SaveAttachmentsToDisk(Item As Outlook.MailItem)
Dim Atmt As Attachment
Dim FileName As String
Dim myExt As String
    For Each Atmt In Item.Attachments
        myExt = Mid(Atmt.FileName, InStrRev(Atmt.FileName, Chr(46)))
        Select Case myExt
            Case ".pdf"
                FileName = "\\AP Invoices for Processing" & _
                           Format(Item.CreationTime, "yyyymmdd_hhmmss_") & Atmt.FileName
                Atmt.SaveAsFile FileName
            Case Else
        End Select
    Next Atmt
End Sub