You seem to be posting this elsewhere too so just linking for answery-goodness.
As one person mentions there: "Air China in Beijing doesn't care. I've seen contracted staff at Air China outstations being pickier, but if you're departing from Beijing you'll be fine.
I've travelled with two carry-on items on Air China. They certainly allow a jacket and a bag. However the obvious solution with a coat/jacket is to just wear it onboard.
I've also flown with a suit bag on many airlines, and taken that onboard in addition to carry-on. (I now have a Skyroll suit bag that I can check instead). What I used to do is walk right up to the customer service manager as I board and say "I was told you would have some place to store this for me? Or can I just put it above my seat?". It's the two options answer - neither was 'no it's not allowed', and most of the time they have offered to store it in a cupboard for me!
You're unlikely to receive flak if you're polite and upfront. Ask how you can resolve the issue together.
It's also worth double checking as you check in - "will they be able to store this for me onboard? Or can I put it above my seat?" will give you another response later - "checked in person said I could bring it on board!".
Again, don't be a jerk about it, but crew are people too and understand that the rules don't fit every single situation, and they don't want angry people on board with them either. They will usually try to help.
Another alternative is to take a digital copy, and get it printed in China? I'm sure your hotel or conference may be able to direct you to a location to print it. Of course, this assumes you have some time to do this in Beijing.