/usr/share/doc/libpcl-segmentation1.8/changelog.gz is in libpcl-segmentation1.8 1.8.1+dfsg1-2ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libpcl-segmentation1.8/../libpcl-common1.8/changelog.gz