Sub rename()
On Error Resume Next
Dim i As Integer
Dim path As String
path = ThisWorkbook.path
For i = 2 To ActiveSheet.UsedRange.Rows.Count
If Dir(path & "\" & "*.pdf") <> "" Then
Name path & "\" & Range("a" & i) & ".pdf" As path & "\" & Range("b" & i) & ".pdf"
End If
Next
End Sub