Hello, Jeff
I hope you are doing well and thanks for reaching out.
You can change the submit text using this filter in your theme’s functions.php file.
add_filter('wpdm_email_lock_form_button_label', 'change_email_lock_submit_button_label', 10, 2);
function change_email_lock_submit_button_label($form_button_label, $package) {
$form_button_label = 'send';
return $form_button_label;
}