I am from Pakistan & living in Beijing. How & where can I apply macau's visit visa ?

You can apply for it at the Beijing Office of Macau SAR government.
First, prepare the required documents including copy of your passport, the application form with a recent passport-style photo glued, proof of your financial standing, transportation arrangement, hotel reservation, your residence permit in mainland PRC and proof of your travel purpose to go there. And then submit the application to Beijing Office to apply for it.