Glad you asked, been doing some research with MrCromeDome and inlined tif's and had some problems.

However with pdf thing work correctly :-],
see working example below

my $in_file = "c:/some/path/chady.pdf";
$|++;
undef $/;
open(IN, $in_file) || die "No open";
binmode(IN);
my $buffer = <IN>;
close(IN);
my $in_file_len = -s $in_file;


binmode(STDOUT);
print <<EOF;
HTTP/1.0 200 OK
Content-Type: application/pdf; name="chady.pdf"
Content-Transfer-Encoding: binary
Content-Disposition: inline; filename="chady.pdf"
Content-Length: $in_file_len

EOF
print $buffer;
[download]

HTH