$ ps -ef | grep "File.pdf"
c0rp     22291 22235 12 12:21 ?        00:00:02 /usr/bin/evince /home/c0rp/File.pdf

$ ps -ef | grep "evince"
c0rp     22291 22235 12 12:21 ?        00:00:02 /usr/bin/evince /home/c0rp/File.pdf

$ lsof -F +p 22291
some other files opened
.
.
.
n/home/c0rp/File.pdf

$ lsof -Fn +p 22291 | grep -i -E "*.pdf$" | sed s/^n//g
/home/c0rp/File.pdf

OUTPUT FOR OTHER PROGRAMS
       When the -F option is specified, lsof produces output that is  suitable
       for  processing by another program - e.g, an awk or Perl script, or a C
       program.
...
...
       These  are  the  fields  that  lsof will produce.  The single character
       listed first is the field identifier.
...
...
            n    file name, comment, Internet address
...
...

$ for ip in $(pgrep -x evince); do lsof -F +p $ip  | grep -oP '^nK.*.pdf$'; done
/home/terdon/file1.pdf
/home/terdon/file2.pdf

$ ps -ef | grep emacs
terdon    6647  6424 23 16:26 pts/14   00:00:02 emacs
terdon    6813  6424  0 16:26 pts/14   00:00:00 grep --color emacs
$ pgrep emacs
6647

$ pgrep -l evince
4606 evince
4611 evinced
4613 evince
$ pgrep -lx evince
4606 evince
4613 evince

ps -ef | grep evince | sed -n '/.*.pdf/p' | sed 's/.*evince (.*)$/1/g'

$ ps -ef | grep evince | sed -n '/.*.pdf/p' | sed 's/.*evince (.*)$/1/g'
/media/avinash/C68C57908C5779BF/pdf/PHP/PHP-Manual.pdf
/media/avinash/C68C57908C5779BF/pdf/python.pdf