Explanation/Reference:
Note:
* From scenario: Changes to confidential documents must be logged.
* Policy features are implemented as programs that run on SharePoint Server 2013. They can be enabled and configured by a server administrator and, when they are enabled, they can be used by site administrators to define policies.
* To implement a policy, associate it with content types, libraries, or lists in sites.
* The top-level site of a site collection includes a Site Collection Policies gallery where administrators of the top-level site can create new policies. After creating a Site Collection policy, you can export it so that administrators of other site collections can import it into their Site Collection Policies galleries. This lets you standardize policies across your organization.
* You can associate a policy with a library, list, or content type in the following ways:
A) Associate policy features with a Site Collection policy and then associate that policy with a content type or with a list or library.
B) Associate a set of policy features directly with a content type, and then add that content type to one or more lists or libraries.
C) Associate a set of policy features directly with a list or library.
Reference: Creating a SharePoint Information Management Policy in 10 Steps The steps you should perform are:
User (NL, 18.05.13):
Create a newpolicy on site collection level.
Associate it with the content type.
Add the content type to the document library.