Please use the following links to download the specification.

OSGi Service Platform Release 4 Version 4.2 Core Specification 
OSGi Service Platform Release 4 Version 4.2 Compendium Specification 
OSGi Service Platform Release 4 Version 4.2 Enterprise Specification 
OSGi Service Platform Release 4 Version 4.2 Core Companion Code 
OSGi Service Platform Release 4 Version 4.2 Compendium Companion Code 
OSGi Service Platform Release 4 Version 4.2 Enterprise Companion Code 
OSGi Service Platform Release 4 Version 4.2 Minimum Execution Environment 
OSGi Service Platform Release 4 Version 4.2 Foundation Execution Environment