21-year old defender Wootton heads to London Road for the remainder of the season with 21-year old midfielder Petrucci joining Darren Ferugson's side until February 9.
"Scott was very unfortunate last time he was here because Ryan Bennett and Gabriel Zakuani struck up such a good partnership, but this time, I am looking for him to be a regular starter," Posh boss Darren Ferguson told the club's official website.
"He has played in a three-man defensive line before and he is very comfortable in any of those positions. I am really pleased to get him, he has been a big part of the squad at United and they think very highly of him."
On Petrucci he added: "Davide is a very good footballer, is a good size and this is his first loan move, so that is why it is only for a month but, between the two of us, I am sure we can extend it to the end of the season if it works out for all parties.
"We need bodies in, I spoke to my Dad (Sir Alex Ferguson - Manchester United manager) about Davide for a couple of weeks and there was other clubs in for him so we are delighted to get him to the football club. My Dad was happy for him and Scott Wootton to join and they will go into the squad for Saturday."