Since you are on *nix, I would recommend alarm and $SIG{ALRM}.

Straight from perldoc:

eval {
        local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required
        alarm $timeout;
        $nread = sysread SOCKET, $buffer, $size;
        alarm 0;
    };
[download]

You can stick your PDF stuff in the sysread line.

CAVEAT: This is not portable to M$ Win32

grep

grep> cd pub grep> more beer