add access is denied for CAD

// Create the CAD Document item

var docItem = MyInnovator.newItem("CAD", "add");
docItem.setProperty("item_number", "CADDoc 004");

// Create the relationship between the CAd Document and File
var relItem = MyInnovator.newItem("CADFiles", "add");
relItem.setFileProperty("attached_file", @"C:\Temp\Test.txt");


var results = docItem.apply();

Iam using above source to create CAD Document, but i get error from server: "add access is denied for CAD"

What do you know about my problem? please!