Michael Smith joined for an undisclosed fee from Bristol Rovers and goalkeeper Ben Alnwick, a free agent who had been on trial with Blackpool, signed a three-year deal with the club.
Ferguson told the club's official website: "Michael Smith is someone we have been tracking for a while. Right-back is a position we knew we had to fill.
"We narrowed the list (of targets) down and Michael was the number one. I think he will be a really good signing, he is a decent age and has played a lot of games in his career. He was in the League Two team of the year and to be voted into that team by your peers is a great accolade.
"He is a great athlete, good technically and one that I believe will be a great signing for us. He was adamant he wanted to come and that was extremely important.
"We are delighted to get Alnwick, we feel with his quality and experience he will make a big difference to us.
"He is really focused and a good age (27), so should be coming up to his peak."
Friday's signings meant Posh had signed three players in the last two days, after securing a loan move for Spurs youngster Kenny McEvoy.
Speaking about his chairman, Ferguson added: "He has been brilliant. The one thing about him (Darragh MacAnthony) is he backs you, when he can.
"We have brought three in this week and feel we are finished unless there is a special one that becomes available.
'The chairman rang me last night at around 9pm and I was actually ready for bed and he told me the goalkeeper was done. It was great, I can't believe how quickly it has been done. I am delighted with the business we have done.
'I thank the chairman for backing me, now it is down to me and my staff to get three or four out to balance the books."