how to add a signature to a pdf file from my WinRT application using Adobe Sign Api

hi,

  I am very new to Adobe Sign Api.. For one of my WinRT application, i need to add an option for adding signatures. right now i have registered with Adobe as a developer and i am working on the available Api and sample code. But i am not successfull in getting a signature on a .pdf file.

My Clarifications are..

1. Is it possible to create an application with Adobe Sign api using developer license.

2. If it is possible, after having client Id, Secret Id & Access Token also why I am getting error at code line,

var transientDocumentResponse = await obj.AddDocument("Doc.pdf", fileBytes);  (Sample code available in Adobe developer guide)

And the error is as below,

"An error occurred while sending the request."

3. If its not possible to creat an app using developer license, what i have to do further to acchive this..

Kindly help me

Thanks,

Ravi M.