/usr/share/doc/docbook-xsl/reference.pdf.gz is in docbook-xsl-doc-pdf 1.78.1-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/docbook-xsl/../docbook-xsl-doc-pdf/doc/reference.pdf.gz
/usr/share/doc/docbook-xsl/../docbook-xsl-doc-pdf/doc/reference.pdf.gz