181+deb9u1) is not available, but a newer one is (181+deb9u2). We redirected you there.
/usr/share/man/man7/postgresql-common.7.gz is in postgresql-client-common 181+deb9u2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man7/../man1/pg_wrapper.1.gz