Visiting China on second time, do I need still to submit complete documents?

I have visited China last April 2013 (7 months ago) for products training of our principals instruments? Now, I have again invitation that I need to attained again the new instrumentation training for the second time. Now in my second application,do I need to submit complete documents again like what I did in my first application? OR invitation letter from my Chinese Principals, application form filled & signed, are sufficient.

Please advise.

From Khalid Khan, Pakistan