De Jong arrived this week from Ajax.
Pardew said: "It's very important for us.
"After Yohan Cabaye left last year we lacked some intelligence to our team in attacking areas. We are absolutely overjoyed to bring him to the club.
"He will give us some intelligence in that last third. He will create situations for us.
"It's something, towards the back end of last year, we struggled with.
"It's a big signing for us and he brings massive experience from Ajax."
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