AFAIK the 5700kg/12,500lbs weight limit is not specified anywhere in EASA Part-FCL. I think it was there when I got my licence over 20 years ago... but I don't know what happened to it. So going back to the pub question, depending on where the PPL was issued it may well be possible to add a 747 type rating to a PPL, provided you meet the other requirements related to operating such a type.