Use below code in theme’s functions.php:

add_action(“gform_user_registered”, “autologin”, 10, 4);
function autologin($user_id, $config, $entry, $password) {
wp_set_auth_cookie($user_id, false, ”);
}

Form more info please find this link: http://www.gravityhelp.com/forums/tags/auto-login

Please find below code to send any documnet, PDF send through mail

/* Gravity forms */
function wdm_add_attachment( $notification, $form, $entry ) {
$upload_dir = wp_upload_dir();
if($form_id==9){
$notification[“attachments”] = $upload_dir[‘basedir’].’/pdf/order_new.pdf’;
}
return $notification;
}

add_filter(“gform_notification”, “wdm_add_attachment”, 9, 3);