Auto create file and send it via wp_mail()

Can’t help you with the creation of the .doc-file, as i have never done that. But if you manage to get the encoded file into a string, you can work with the WordPress PHP-Mailer instance like this:

function send_my_mail_with_attachment($from,$to,$subject,$body,$attachmentstring=""){
        global $phpmailer;
        // (Re)create it, if it's gone missing
        if ( ! ( $phpmailer instanceof PHPMailer ) ) {
            require_once ABSPATH . WPINC . '/class-phpmailer.php';
            require_once ABSPATH . WPINC . '/class-smtp.php';
            $phpmailer = new PHPMailer( true );
        }
        $phpmailer->CharSet="UTF-8";
        $phpmailer->ClearAllRecipients();
        $phpmailer->ClearAttachments();
        $phpmailer->ClearCustomHeaders();
        $phpmailer->ClearReplyTos();
        $fromaddress=$from;
        $phpmailer->setFrom($fromaddress);
        $phpmailer->Sender = $phpmailer->From;
        $phpmailer->addAddress($to);
        $phpmailer->isHTML(true);   // Set email format to HTML
        $phpmailer->Subject = $subject;
        $phpmailer->Body    = $body;
        if($attachmentstring){
               $phpmailer->AddStringAttachment($attachmentstring,'my_attachment.doc');
        }
        $rueckgabe = $phpmailer->Send(); 
        return $rueckgabe;
}

You can learn more about PHPMailer here