New cloud based app - suggest database schema improvements / use of existing source etc

I have previously worked as a programmer many years ago and did basic web based database integration. I am close to finishing a database schema for a new business idea. Based on my research, I am looking at a mySQL backend and PHP server side script. Part of the app would be available to the public via a website but most of the functionality would be for employees in the busines, so security is an issue. Current expectation is that the internal functionality for employees etc would be designed for a mobile app (HTML output would be sufficient). Also, there will be automation issues that need consideration - in particular, the system will need to: (1) manage version control of word documents created internally; (2) take website users' details, generate agreements from those details and email PDF of that agreement to the customer (while updating the database with a record of those agreements); (3) integrate with DropBox (e.g. to file final agreements from item (2) to a DropBox folder) etc. The database has been designed on the premise that much of this work will be developed from scratch, but there are likely to be existing applications that will assist and part of the freelancer's role will be to identify existing code that might achieve the goal without needing to re-invent the wheel. Finally, the freelancer may be employed to assist in managing the developer chosen to develop the application and choosing a suitable hosting environment. Some experience with DropBox integration (or at least an understanding of how it works) would be useful. For example, when a new record is inserted in the database, the app would send a command to DropBox to create a folder etc. Freelancers should have exceptional skills in database deisgn and server side scripting and security and should identify relevant work that hthey have done in the past. Good communication is critical. I am time poor so if the person proves to be exceptional at what they do, there will be ongoing work to administer the development of the app.