/usr/lib/x86_64-linux-gnu/libqpdf.so.21 is in libqpdf21 8.0.2-3~16.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libqpdf.so.21.0.2
/usr/lib/x86_64-linux-gnu/libqpdf.so.21.0.2