Leonardo: Landing Motta a pleasant surprise
"He's a great player... it's a big signal to our fans," Leonardo told a news conference on Wednesday. "I am very happy he signed.
"Thiago will now earn less than he used to at Inter. It was a last-day surprise, even for us. His will to come here counted for a lot."
The Italy midfielder was the final major signing of the window for wealthy PSG who last month also snapped up full-back Maxwell from Barcelona and Chelsea centre-half Alex.
According to media reports, the Ligue 1 leaders paid 10 million euros for Thiago Motta, 29, who has been capped six times by his country.
Since Qatar Sports Investment bought the club last May, PSG have spent more than 100 million euros on new players including 42 million for Palermo and Argentina playmaker Javier Pastore in August.
"PSG are now the sort of the club who can sign great players," said Brazilian Leonardo.
The leaders, who are three points ahead of second-placed Montpellier, entertain Evian Thonon Gaillard in the league on Saturday.