/usr/bin/ViewPDF is in viewpdf.app 1:0.2dfsg1-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/bin/../lib/GNUstep/Applications/ViewPDF.app/ViewPDF
/usr/bin/../lib/GNUstep/Applications/ViewPDF.app/ViewPDF