Split to Top-Level Bookmark is not working in Acrobat DC. To "solve" the problem, the user has to uninstall Acrobat DC, then re-install. Now the process works, but only once. The user then has to repeat the uninstall / re-install process to use the feature again. Else, the user gets the error message "The file may be read-only, or another user may have it open. Please save the document with a different name or in a different folder." This feature MUST work without the user having to uninstall / reinstall Acrobat DC.