use CGI;

my $f;

open (OUT,"somefile.pdf") or print STDERR "Can't open $!";
while (<OUT>) { $f .= $_; }
close (OUT);

my $l = length($f);

print CGI->header(
        -type =>"application/octet-stream",
        -expires=> '+3d',
        -charset=>'utf-7',
        -Content_length => $l,
        -attachment => "example.pdf",
);

print $f;

exit;