Sub PSize()
Dim A3 As Integer
Dim A4 As Integer
Dim i As Long
Dim R As Range

    A3 = 0
    A4 = 0
    Set R = ActiveDocument.Range
    For i = 1 To R.Information(wdActiveEndPageNumber)
        Set R = ActiveDocument.GoTo(What:=wdGoToPage, _
                                    Which:=wdGoToAbsolute, _
                                    Count:=i)
        Select Case R.PageSetup.PaperSize
            Case wdPaperA3
                A3 = A3 + 1
            Case wdPaperA4
                A4 = A4 + 1
        End Select
    Next
    Debug.Print "Общее число страниц А1 = " & A4 / 8+ A3 / 4

End Sub