/usr/lib/puredata/doc/7.stuff is in puredata-core 0.45.4-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/puredata/doc/../../../share/puredata/doc/7.stuff
/usr/lib/puredata/doc/../../../share/puredata/doc/7.stuff