Close a PDF file that is opende with vba

Hello

i open a PDF file witrh this but how to close it

Function OpenAnyFile(strPath As String)
  Set objShell = CreateObject("Shell.Application")
  objShell.Open (strPath)
End Function

Sub Open_Ferieplan()
  Dim pdfPath As String
  pdfPath = "O:\EMV KS-System NS-EN 9001\EMV Arbeidsbøker\EMV Ferieplan\Ferieplan.pdf"
  Call OpenAnyFile(pdfPath)
End Sub