/usr/share/doc/pangomm-1.4 is in libpangomm-1.4-doc 2.28.4-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libpangomm-1.4-doc
/usr/share/doc/libpangomm-1.4-doc