procedure TForm1.frxReport1EndDoc(Sender: TObject);
var p: TfrxReportPage;
    m: TfrxMemoView;
    i: integer;
begin
     frxReport1.Preview.Lock;
     for i := 0 to frxReport1.PreviewPages.Count - 1 do
       begin
         p:=TfrxReportPage(frxReport1.PreviewPages.Page[i]);
         m:=TfrxMemoView.Create(p);
         m.CreateUniqueName;
         m.SetBounds(0, 0, (p.PaperWidth  - p.RightMargin - p.LeftMargin) * fr01cm, (p.PaperHeight - p.TopMargin - p.BottomMargin) * fr01cm);
         m.Text := 'Demo';
         m.Rotation := 45;
         m.Font.Size := 128;
         m.VAlign := vaCenter;
         m.HAlign := haCenter;
         frxReport1.PreviewPages.ModifyPage(i,p);
       end;
     frxReport1.Preview.UnLock;
end;

procedure TForm1.FormCreate(Sender: TObject);
var m: TfrxMemoView;
    i, j: integer;
    p: TfrxReportPage;
    c: TObject;
begin
  frxReport1.PrepareReport();
  for i := 0 to frxReport1.PreviewPages.Count - 1 do
  begin
    p := frxReport1.PreviewPages.Page[i];
    for j := 0 to p.AllObjects.Count - 1 do
      begin
        c := p.AllObjects.Items[j];
        if c is TfrxMemoView then
          begin
            m := TfrxMemoView(c);
            if m.TagStr = 'test' then
              begin
                m.Memo.Text := 'Test';
                frxReport1.PreviewPages.ModifyObject(m);
              end;
          end;
      end;
  end;
  frxReport1.ShowPreparedReport();
end;