what document require for renew " L " type visa ?

I already join my wife ( she is chinese National ) here in china, i got " L" visa from pakistan, so what document i need to renew this visa so long terms stay with my wife here in china? Does i can apply same time change this visa to do my own business or work here in china ? so what document i require ? please give me answer with detail, thank you very much your kind help all time