Yes, you should not expect perfect documentation for SDKs, you have to be a little bit creative (is valid also for Adobe InDesign or QuarkXPress). In your case the second parameter was a strong hint for me to expect the return value as a CGContextRef. I just tried and it did work!
For building a plug-in for Acrobat DC use the Acrobat 11 SDK and set the target architecture to 64 bit! You can also build universal binaries for Acrobat 9 and later (one binary for different versions of Acrobat).