Sub UpdateDocuments()
Application.ScreenUpdating = False
Dim strFolder As String, strFile As String, wdDoc As Document
strFolder = GetFolder
If strFolder = "" Then Exit Sub
strFile = Dir(strFolder & "\*.doc", vbNormal)
While strFile <> ""
  Set wdDoc = Documents.Open(FileName:=strFolder & "\" & strFile, AddToRecentFiles:=False, Visible:=False)
  With wdDoc.Sections(1).Footers(wdHeaderFooterPrimary).Range
    .Text = "My Footer Text"
    With .Font
      .Size = 15
      .Name = "Arial"
      .Bold = True
    End With
  End With
  wdDoc.Close SaveChanges:=True
  strFile = Dir()
Wend
Set wdDoc = Nothing
Application.ScreenUpdating = True
End Sub
Function GetFolder() As String
Dim oFolder As Object
GetFolder = ""
Set oFolder = CreateObject("Shell.Application").BrowseForFolder(0, "Choose a folder", 0)
If (Not oFolder Is Nothing) Then GetFolder = oFolder.Items.Item.Path
Set oFolder = Nothing
End Function