How can send PDF attachment in `Node aws-sdk` sendRawEmail function?

I want to send a PDF file in an attachment using the sendRawEmail(Node: aws-sdk) function. I have tried lots of ways. The email is send successfully, but the PDF goes plain.

How can my code be corrected?

The code is here:

try {
    data = fs.readFileSync('files/demo-invoice-new.pdf', 'utf8');

    console.log(data.toString());

    var ses_mail = "From: 'AWS SES Attchament Configuration' <" + SOURCE_EMAIL + ">\n";
    ses_mail = ses_mail + "To: " + toEmail + "\n";
    ses_mail = ses_mail + "Subject: AWS SES Attachment Example\n";
    ses_mail = ses_mail + "MIME-Version: 1.0\n";
    ses_mail = ses_mail + "Content-Type: multipart/mixed; boundary=\"NextPart\"\n\n";
    ses_mail = ses_mail + "--NextPart\n";
    ses_mail = ses_mail + "Content-Type: text/html; charset=us-ascii\n\n";
    ses_mail = ses_mail + "This is the body of the email.\n\n";
    ses_mail = ses_mail + "--NextPart\n";
    ses_mail = ses_mail + "Content-Type: application/octet;\n";
    ses_mail = ses_mail + "Content-Disposition: attachment; filename=\"demo-invoice-new.pdf\"\n\n";
    ses_mail = ses_mail + data.toString('utf8') + "\n\n";
    ses_mail = ses_mail + "--NextPart--";

    var params = {
        RawMessage: { Data: new Buffer(ses_mail) },
        Destinations: [toEmail],
        Source: "'AWS SES Attchament Configuration' <" + SOURCE_EMAIL + ">'"
    };

    console.log(params);

    var sendPromise = new AWS.SES(AWS_SES_CONFIG).sendRawEmail(params).promise();

    return sendPromise.then(
        data => {
            console.log(data);
            return data;
        }).catch(
        err => {
            console.error(err.message);
            throw err;
        });
} catch (e) {
    console.log('Error:', e.stack);
}

SES raw messages must be base64-encoded. So, you'll need to get the file content as buffer and encode it as Base64 string attachment. Also, you don't need to create a new buffer for raw message data since it already accepts a string data type.

Optional: You can also omit the Destinations parameter since you're already providing the To field in the raw message data. (You can also provide the Cc and Bcc fields as well.)

You could try this for example:

data = fs.readFileSync("files/demo-invoice-new.pdf");

var ses_mail = "From: 'AWS SES Attchament Configuration' <" + SOURCE_EMAIL + ">\n";
ses_mail += "To: " + toEmail + "\n";
ses_mail += "Subject: AWS SES Attachment Example\n";
ses_mail += "MIME-Version: 1.0\n";
ses_mail += "Content-Type: multipart/mixed; boundary=\"NextPart\"\n\n";
ses_mail += "--NextPart\n";
ses_mail += "Content-Type: text/html\n\n";
ses_mail += "This is the body of the email.\n\n";
ses_mail += "--NextPart\n";
ses_mail += "Content-Type: application/octet-stream; name=\"demo-invoice-new.pdf\"\n";
ses_mail += "Content-Transfer-Encoding: base64\n";
ses_mail += "Content-Disposition: attachment\n\n";
ses_mail += data.toString("base64").replace(/([^\0]{76})/g, "$1\n") + "\n\n";
ses_mail += "--NextPart--";

var params = {
    RawMessage: {Data: ses_mail},
    Source: "'AWS SES Attchament Configuration' <" + SOURCE_EMAIL + ">'"
};

Note: The /([^\0]{76})/ regular expression replacement breaks your long lines to make sure that mail servers do not complain about message lines being too long when there is an encoded attachment, which might result in a transient bounce (see RFC 5321).