The SPS Document Library service enables storage and management of documents. If this service is stopped document management and collaboration features such as publishing and feedback will be unavailable.
A service can stop for many reasons, including
The service was stopped by an Administrator.
The service encountered an exception that stopped the service.
The service was improperly configured, which prevented it from starting.
The service was prevented from starting because the user account assigned to the service could not be authenticated.
The service can be restarted using the Start SPS Document Library Service task:
Start Document Library Service
If service is unable to restart successfully please refer to the tasks output which will indicate the cause for the start failure. With this information, the Services snap-in from the Computer Management console can be used to take additional resolution steps:
Start Computer Management Console