I guess I'm almost there, but getting an error saying invalid annotation object. Something wrong in the PDAnnotNotifyDidChange? Does that key suppose to be something else?
CosObj cosDict = CosNewDict(cd, true, 4);
CosDictPutKeyString(cosDict, "Subtype", CosNewNameFromString(cd, false, "Highlight"));
CosDictPutKeyString(cosDict, "QuadPoints",ArrayObj);
pdAnnot = PDAnnotFromCosObj(cosDict);
PDAnnotNotifyDidChange( pdAnnot, ASAtomFromString( "Highlight" ),0 );
PDAnnotSetColor(pdAnnot, &red);
AVPageViewDrawNow (currentPageView);
PDPageRelease (pdPage);