Error: "Cannot open database "WSS_Content_...." requested by the login. The login failed. Login failed for user ... "

Today I am converting word to PDF file using Word Automation Service, its throw error like "Cannot open database "WSS_Content_...." requested by the login. The login failed. Login failed for user ... "

Solution :

I have open IIS manager and click on the Application pool. Selected respected site's pool and apply valid user authentication over there. After reset IIS and checked my feature.

Its Working...

Enjoy...