What documents I required to get my Visa? Or I should contact the agents or can I apply directly to the embassy or consulate?

Mir, individual Pakistanis can't apply for individual L type for visiting PRC. They need to join group tours arranged by qualified travel agencies. So you either join a group tour or apply for other types, M for example. It asks for more documents including invitation letter or confirmation letter made by duly authorized unit in PRC, invitation letter from your Chinese business partner, guarantee letter from your company, tax certificate and copy of your company license, the recent six months' bank bill and round-trip air tickets and hotel booking in PRC (if you come to PRC for the first time).