We are introducing a new public API that is designed to be implemented easily. Those who are using previous version of the API (below 19.9), you don’t have to worry. The legacy API has been moved into legacy namespace. If you want to upgrade to v19.9, it is required to make project-wide Replacement of namespace usages from GroupDocs.Conversion to GroupDocs.Conversion.Legacy in order to avoid any build issues.
Why to use new version?...required to make project-wide replacement of namespace usages from...