/usr/bin/xfig-pdf-viewer is in xfig-doc 1:3.2.5.c-3.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 | #! /bin/sh
#
# $Id: xfig-pdf-viewer,v 1.6 2014/05/13 16:04:34 roland Exp $
#
##########################################################################
#
# xfig-pdf-viewer is a little shell script, which tries to find out
# which PDF viewer you have installed on your system and then starts
# them. The environment variable PDFVIEWER has priority over all other
# viewers.
# See xfig-pdf-viewer(1) man page for more information.
#
##########################################################################
#
#   Copyright (C) 1999-2014  Roland Rosenfeld <roland@spinnaker.de>
#
#   This program is free software; you can redistribute it and/or
#   modify it under the terms of the GNU General Public License as
#   published by the Free Software Foundation; either version 2 of
#   the License, or (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
#   General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
#
##########################################################################
if [ "$1" = "-n" ]; then
    echo "No viewer found in xfig-pdf-viewer(1), please set PDFVIEWER"
    echo "environment variable or install a PDF viewer"
    read dummy
    exit 0
fi
if [ $# -ne 1 ]; then
    echo "Usage: $0 file.pdf"
    exit 0
fi
if [ "$PDFVIEWER" != "" ]; then
    :
elif type xpdf >/dev/null 2>&1; then
    PDFVIEWER=xpdf
elif type okular >/dev/null 2>&1; then
    PDFVIEWER=okular
elif type evince >/dev/null 2>&1; then
    PDFVIEWER=evince
elif type acroread >/dev/null 2>&1; then
    PDFVIEWER=acroread
elif type ViewPDF >/dev/null 2>&1; then
    PDFVIEWER=ViewPDF
elif type gv >/dev/null 2>&1; then
    PDFVIEWER=gv
elif type zathura >/dev/null 2>&1; then
    PDFVIEWER=zathura
elif type epdfviewer >/dev/null 2>&1; then
    PDFVIEWER=epdfviewer
else
    exec x-terminal-emulator -e $0 -n
fi
exec $PDFVIEWER "$1"
 |