How to set page size with rave report

I have a project in Delphi 2010 and I'm using RaveReport to generate PDF reports through the code, my question is I want to know if it is possible and how can I set the size (height and width) of my PDF page.

I tried it but did not resulted:

var PWidth: Double;

PWidth := 20;
System.BaseReport.PageWidth := PWidth;

And tried this:

System.BaseReport.SetPaperSize(DMPAPER_USER, 2100, 1400); 

Any solution?

Solution for my problem:

procedure TfrmLogger.RvSystemBeforePrint(Sender: TObject);
begin
  with Sender as TBaseReport do
    begin
      Units := unInch;
      UnitsFactor := 1;
      SetPaperSize(DMPAPER_USER, 21, 29.7);
      Units := unCM;
      UnitsFactor := 2.54;
    end;
end;