Each content type in a document library can be assigned an individual document templates. In the document library below, two different content types have been added, each with a different template.
To edit the word templates, open the site in SharePoint designer 2013.
Open the document library.
In the content types section, open the content type (in this case it is called Policy).
In the ribbon select “Edit Document Template”.
This will allow you to create a dotx document which will be the template for this particular content type in this library. Once the template has been saved, it will be available as the main template for the content type.
When users create a document using the Policy content type from the new menu, it will prompt them to enter a name for the new document.
Please note that currently, the new templates will only open in Office Web Apps (online) if using Internet Explorer. Other browsers will prompt to open in the client application.