Unable to invoke https request from flex application embedded in pdf file

I have a flex application that I embed in a pdf file. This application makes an https request to a web service to get some data. I'm using <mx:HTTPService> to make this call. When I run the standalone swf file in a browser, I'm able to get the results from the web service. However, when I embed the swf file in a PDF file, and open it in Adobe reader, the web service call fails with the following message:

faultCode:Channel.Security.Error

faultString:'Security error accessing url'

faultDetail:'Destination: DefaultHTTP'