Comprehensive Web Development Project with Document Management

Hi I am looking for a cloud based web solution for document storage and management. I have a process wherein we do real estate developer approvals. The basic flow is

Step 1 : Client specifies real estate developer
Step 2: I collect a long list of documents and am supposed to digitize them
Step 3: I send these documents to a technical and a legal agency for due diligence (both a separate)
Step 4: They send additional list of documents if required , for which I go to step 2
Step 5: If there is no step 4, these agents give their opinion
Step 6: I provide these to the client

Needless to say that I am technologically challenged and thus this post

Is there any comprehensive solution that I can look at, happy to pay !!