Private Declare Function ShellExecute Lib "shell32.dll" _
    Alias "ShellExecuteA" (ByVal hWnd As Long, _
    ByVal lOperation As String, _
    ByVal lpFile As String, _
    ByVal lpParameters As String, _
    ByVal lpDirectory As String, _
    ByVal nShowCmd As Long) As Long
 
Private Declare Function GetActiveWindow Lib "user32" _
  Alias "GetActiveWindow" () As Long

ShellExecute GetActiveWindow(), "print", "Pfad+Name der pdf-Datei", "", "", _
  vbHide