/usr/lib/x86_64-linux-gnu/libptexenc.so.1 is in libptexenc1 2017.20170613.44572-8ubuntu0.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libptexenc.so.1.3.5
/usr/lib/x86_64-linux-gnu/libptexenc.so.1.3.5