How to Programmatically Attach a File to Email Notifications

add_filter( 'wpforms_emails_mailer_get_attachments', function( $attachments, $mailer ) {

    // Get the uploads directory path.

    $upload_dir = wp_upload_dir();

   // Add your custom file path(s)

    $file_url = '/path/to/your/file.pdf';

    // Convert URL to local file path.

    $file_path = str_replace( $upload_dir['baseurl'], $upload_dir['basedir'], $file_url );

    // Check if the file exists on the server.

    if ( file_exists( $file_path ) ) {

        $attachments[] = $file_path;

    }

    return $attachments;

}, 10, 2 );