addin to update footer

need a addin which will ask for document type and update the footer with that eg. confidential or internal

No add-in needed, you'll have to make a userform with two option buttons (Confidential / Internal) and then set their action as follows :

Private Sub OptionButton1_Click()
ActiveSheet.PageSetup.CenterFooter = "CONFIDENTIAL"
End Sub
Private Sub OptionButton2_Click()
ActiveSheet.PageSetup.CenterFooter = "INTERNAL"
End Sub

I assume you want to show the popup before print or something, so in the worksheet code, set :

Private Sub Workbook_BeforePrint(Cancel As Boolean)
UserForm1.Show
End Sub

Please click the * below if this helps