Dim filename As String
Const FILEPATH As String = "\\SERVER\Billing\"
filename = FILEPATH & Format(Date, "yyyymmdd") & "_" & [Mdid] & ".pdf"
' or
filename = FILEPATH & [Mdid] & "_" & Format(Date, "yyyymmdd") & ".pdf"
Debug.Print filename
DoCmd.OutputTo acOutputReport, , acFormatPDF, filename