I'm rather late to the party, but how do you actually receive the .hl file? I've recently bought the pdf but the zip didn't include the .hl file, or is that no longer a thing?
The most current version of the Dragonrider is located in the Pathfinder 3PP Pack (a free community download) for HL. This pack requires the official HL licenses Advanced Players Guide, Ultimate Combat, and Ultimate Magic but it contains dozens of 3PP books including many SGG/RGG class, feats, and spells.
Follow the above link to the LW Forums where you can find full details on how to install.