The 35-year-old has been signed to provide competition for first choice goalie Tommy Evans.
Iron manager Brian Laws said: "In the past we have only worked with one professional keeper but after last season we feel we needed to strengthen in that area.
"Paul is very commanding in his box and has a lot of experience to pass on to the other players.
"The two goalkeepers will have to battle it out for the number one spot and we have already seen when we have brought someone in it brought the best out of Tommy Evans."
He made 132 appearances for the club between 1988 and 1992.
The club are also expecting to complete a deal for an experienced midfielder tomorrow.