Since the Link to a Document content type functions just like any other content type in SharePoint, it can be extended to include additional columns that other library content types might be using. This allows for a consistent UI design and allows for the Link to a Document’s content to be displayed along with the rest of the content and filtered and sorted as necessary.
Additional columns can be added to the content type. This section describes how to do so in SharePoint 2010.
Click Site Actions and select Site Settings.
From the Site Settings menu, click the Site Content Types link in the Galleries section (see Figure 9-17).
Figure 9-17. Click Site content types in Site Settings
Click the Create option to start the process of creating a new Link to a Document content type. Give the new content type a name and description. Select the parent category as Document Content Types and the parent as Link to a Document. You can create a new group if you’d like or just accept the default of Custom Content Types. When finished, click OK (see Figure 9-18).
Figure 9-18. Creating a new content type based on an existing content
When you click OK, you’ll be shown the details page for that content type.
From here there ...