my $PDF = ...; # read PDF binary contents from file
my $LOGSTR = ...; # read LOG file contents
use MIME::Base64;
my $data = {
  # this is binary that's why we encode it to fit in a JSON string
 'pdf' => encode_base64($PDF),
  # this is text but it does not harm:
 'logstr' => encode_base64($LOGSTR)
};
# send the data to client:
# CGI version:
use CGI qw(:standard);
use JSON;
print header('application/json');
my $json_text = to_json($data);
print $json_text;

# OR render JSON to go to client with Mojolicious
my $c = ... # controller
...
$c->render(json => $data); # $data as above