How to return a PDF from a Web API application

I have a Web API project that is running on a server. It is supposed to return PDFs from two different kinds of sources: an actual portable document file (PDF), and a base64 string stored in a database. The trouble I’m having is sending the document back to a client MVC application. The rest of this is the details on everything that’s happened and that I’ve already tried.

Invalid object name ‘dbo.AspNetUsers’ in Asp.NET MVC 5 Entity Framework

If you have an existing database, and you want to include ASP.NET Identity tables to it, you can face this error. You may not know how to integrate [AspNetRoles], [AspNetUserClaims], [AspNetUsers], [AspNetUserLogins] tables into your existing database when you start. Although there are a lot of resources about this topic, this answer tries to be short and to the point. You may want to use the Database-First approach in Entity Framework together with the ASP.NET Identity feature of ASP.NET MVC. This is a very short tutorial for dummies. I am sorry if my English is poor.