I have been invited for a conference where all my expenses are born by the organizers.

Hi,
I've visited China in 2013 September for a conference as well. I've received an invitation letter from the company to attend the meeting, which also indicate that they are covering my accommodation and other expenses.
When I submitted this letter for visa, my travel agent has been told I need another letter.
I have informed them about this and they are in the process of arranging it. Do I need the original or will a scanned copy suffice?