I say yes.
The definition of a configuration item is: entity that can be uniquely identified at a given reference point
(So no exclusion there). Then 8.1.1 says:
The MANUFACTURER shall establish a scheme for the unique identification of CONFIGURATION ITEMS and their VERSIONS to be controlled for the project. This scheme shall include other SOFTWARE PRODUCTS or entities such as SOUP and documentation. [Class A, B, C]
(Still no exclusion)
And finally, 8.1.3 (note placement under 8.1 Configuration Identification):
8.1.3 Identify SYSTEM configuration documentation
The MANUFACTURER shall document the set of CONFIGURATION ITEMS and their VERSIONS that comprise the SOFTWARE SYSTEM configuration. [Class A, B, C]
(Rather explicit INCLUSION, I'd say.)
That said, documents are generally managed through Doc Control; i.e., not so much under the SCM system. So the point is to ensure proper configuration control over everything that goes into the software system.