Making HTTP request in the PDF

Hello there, 

I am trying to make a pdf button where i can click on it , retrieve the data from the server , fill a dropdown list from there.

The code : 

Net.HTTP.request({
cVerb: "GET",
cURL: "http://newits.devs/getContacts.php",
oHandler:{
response: function(msg,uri,e,h){
    app.alert(msg);
}
}
});

But i am getting an error after i click it : 

NotAllowedError: Security settings prevent access to this property or method.