Hello, some suggestions as below:
1) Could you please sign these documents for proceeding? = 可否簽閱此等文件作跟進之用呢?
2) Kindly sign the document for the confirmation on goods supplied. = 敬請簽閱此文件作確實供貨之用。
3) Please approve & sign the cheque for payment arranged. = 請批閱及簽妥此支票作付款之用。