LoadFromFile return 0

Please,
i have no idea why LoadFromFile, sometimes returns 0.
These .pdf files are generated by a Brother Scanner (may be this is the matter). They are well opened by Acrobat Reader and other readers.

Here my sample code:

procedure TForm1.Button1Click(Sender: TObject);
var
PDFLibrary: TQuickPDF0721;
UnlockResult: Integer;
risultato : integer;

begin
  WebBrowser1.Navigate('c:\I300.pdf'); <<<<< I300.pdf is shown >>>>>>>>>>>
  PDFLibrary := TQuickPDF0721.Create;
  try
    UnlockResult := PDFLibrary.UnlockKey('mykey');
    if UnlockResult = 1 then
      begin
        risultato := PDFLibrary.LoadFromFile('c:\I300.pdf');
        showmessage(inttostr(risultato)); <<<<<<<<< "0" is shown >>>>>>>>>>>>>>>>
        PDFLibrary.SaveToFile('C:\test.pdf');<<<<<<<<< empty document >>>>>>>>>>>
      end
    else
      begin
        ShowMessage('Invalid license key');
      end;
  finally
     PDFLibrary.Free;
  end;
end;

Here the I300.pdf:
www.winsvetta.com/QP/I300.zip

I can't figure out how can solve. Please, HELP.

Thx
Giovanni

Thx Rowan
I was almost sure about Brother responsability. You confirm my hypothesis but, more, your declaration helps me to prove to customer that the malfunction is not the fault of my software.

thx again
Giovanni