You are misunderstanding the directions. The sentence is "To enable your plug-in for Adobe Reader XI, you must update AcroDspOptions.rsp by removing the acrocolorHFT define and adding the READER_PLUGIN define. " You do NOT want to do this, because you do NOT want to enable your plug-in for Adobe Reader. Many of the methods in the snippets will not work with Reader, and will (correctly) produce compile errors exactly like the one you quote.
So you are left with the HFT problem for ACROCOLOR, however, this is not the solution.