/**
 * Save PDF link of entry, as user as user meta
 */
add_action( 'caldera_forms_submit_complete', function( $form, $referrer, $process_id, $entry_id ) {
    //change your form ID here
    if( 'cf123..' != $form[ 'ID' ] ) {
        return;
    }

    $message = \calderawp\calderaforms\pro\container::get_instance()->get_messages_db()->get_by_entry_id( $entry_id );
    if( ! is_wp_error( $message ) ) {
        $link = $message->get_pdf_link();
        update_user_meta( get_current_user_id(), '_last_entry_pdf', $link );
    }

}, 10, 4 );