如何将任何文件下载到任何设备并查看？

The below code is an API call in which I'm passing a documentID and I'm trying to open a document. Due to the fact that this whole process is running on a server I'm not able to view the file on any other device(be it another desktop or mobile device) although the file will open up in server machine but wont open locally. Can anyone please guide me through as to where I'm going wrong ? (sorry for the code, I know it might not be perfect as I'm new to web dev. still learning).The below code is an API call in which I'm pass