The description for the location of SDK as written in this post and in Server help is confusing. I installed ArcGIS Server 10.2 and the GeoEvent Processor Extension using the ISO file downloaded from the ESRI Customer Care Portal. I mounted the ISO file to a virtual DVD drive in VMware 10.x. If you mount the ISO file like I did then use Windows explorer and browse to <CD-DVD DRIVE LETTER>:\GeoEventProcessor\SDK\GeoEventProcessor-SDK-10.2.zip" . You can also use the utility named 7Zip to extract the ISO file to a windows folder. The SDK can then be located at ..\ArcGIS_Server_Ent_Windows_102_134934\GeoEventProcessor\SDK\GeoEventProcessor-SDK-10.2.zip.
Dennis Geasan
GIS Technologies.