/usr/lib/libatrildocument.so is in libatrildocument-dev 1.8.1+dfsg1-4+deb8u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/libatrildocument.so.3.0.0
/usr/lib/libatrildocument.so.3.0.0