Are you looking for a software or script solution? Programmatically, see Starting Services ( LSCopyAllRoleHandlersForContentType()for example). For scripting, you probably want lsregisterone that is buried in
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Support
Do not let your location in the documents fool you. This is in Carbon docs, but in fact it is CoreServices that are not out of date.