/usr/share/man/man3/i2d_X509.3ssl.gz is in libssl-doc 1.0.2g-1ubuntu4.15.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man3/d2i_X509.3ssl.gz
/usr/share/man/man3/d2i_X509.3ssl.gz