how to change scribd doc permissions??

Question

I have uploaded a file. Now I want to disable the downloading. I used the doc.changeSettings function. I have the reference of parameters here.

I want to know does the parameter passing order is necessary, the order as given by the above url.

My code is as follows:

$doc_ids = array("xxxxxxxxxx");
$title = "LC6";

$description = "Updated Description";

$access = "private"; 

$license = "pd"; //public domain.. c for normal copyright.. ect.

//$parental_advisory = "adult";

$show_ads = "false"; // setting this to "default" will use the configured option in your account

//$tags = "tag, another tag, another tag"; //You can also use an array here
$download_formats = "";

$data = $scribd->changeSettings($doc_ids, $title, $description, $access, $license, $parental_advisory, $show_ads, $tags, $download_formats); //returns 1

But this code is not changing the permissions and download link is still enable. Any clue?