/usr/include/ is in okular-dev 4:4.8.2-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/okular/
/usr/include/okular/interfaces/
/usr/include/okular/interfaces/configinterface.h
/usr/include/okular/interfaces/viewerinterface.h
/usr/include/okular/interfaces/printinterface.h
/usr/include/okular/interfaces/guiinterface.h
/usr/include/okular/core/
/usr/include/okular/core/utils.h
/usr/include/okular/core/form.h
/usr/include/okular/core/pagesize.h
/usr/include/okular/core/fileprinter.h
/usr/include/okular/core/document.h
/usr/include/okular/core/textpage.h
/usr/include/okular/core/sourcereference.h
/usr/include/okular/core/version.h
/usr/include/okular/core/global.h
/usr/include/okular/core/page.h
/usr/include/okular/core/pagetransition.h
/usr/include/okular/core/action.h
/usr/include/okular/core/okular_export.h
/usr/include/okular/core/generator.h
/usr/include/okular/core/fontinfo.h
/usr/include/okular/core/annotations.h
/usr/include/okular/core/area.h
/usr/include/okular/core/textdocumentgenerator.h
/usr/include/okular/core/sound.h