procedure pdfTest(AWriteText: boolean);
var LOcrText: string;
    LPDF    : TDebenuPDFLibrary;
begin
  LPDF := TDebenuPDFLibrary.Create;
  LPDF.UnlockKey('your key');
  try
    LPDF.SetPDFAMode(2);
    LPDF.SetMeasurementUnits(1);
    LPDF.SetPageSize('A4');
    LPDF.CompressImages(1);
    LPDF.AddImageFromFile('g:\temp\test.tif', 1); // use Windows Paint, draw a line for example and save as Tiff
    LPDF.FitImage(0, LPDF.PageHeight, LPDF.PageWidth, LPDF.PageHeight, 1, 1, 0);  //or  LPDF.DrawScaledImage((...

    { if AWriteText is true or just one of the three lines is executed, the file size is > 1000 kB }
    { if AWriteText is false the file size is only ~ 13 kB  }
    if AWriteText then begin
      LOcrText := 'this is only a test test';
      LPDF.SetTextMode(3); // Invisible text
      LPDF.SetTextSize(6);
      LPDF.DrawTextBox(5, LPDF.PageHeight-5, LPDF.PageWidth-10, LPDF.PageHeight-10, LOcrText, 1);
    end;

    LPDF.SaveToFile('g:\temp\test.pdf');
  finally
    LPDF.Free;
  end;
end;