[NumLock]

Код:

type
  TForm1 = class(TForm)
    PageControl1: TPageControl;
    Panel1: TPanel;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
...
procedure TForm1.Button1Click(Sender: TObject);
var
  ATabSheet: TTabSheet;
  ARichEdit: TRichEdit;
begin
  ATabSheet:=TTabSheet.Create(PageControl1);
  ATabSheet.PageControl:=PageControl1;
  ATabSheet.Caption:='Файл '+IntToStr(Tag);
  Tag:=Tag+1;
  ARichEdit:=TRichEdit.Create(ATabSheet);
  ARichEdit.Parent:=ATabSheet;
  ARichEdit.Align:=alClient;
end;