This topic describes the following aspects of using the Microsoft Office PIAs in Office projects: In some scenarios, you might need to add references to additional PIAs (for example, if you want to use a feature of Microsoft Office Word in a project for Microsoft Office Excel). When you create a new Office project, Visual Studio adds references to the PIAs that are required to build the project. The PIA enables managed code to interact with a Microsoft Office application's COM-based object model.
And finally I deleted .dll reference in the project and added. Which Microsoft Word (and Excel) Interop Assembly or DLL.
