Rikus,
As Thunor says, it's hard for most of us (with or without ADD) to respond in a cool calm collected manner when we're under pressure. I believe it's called performance anxiety.
Learning ways to recognize the signs of being stressed, and learning relaxation practices (easier said than done!) can, over time, be a big help here. Also, as Thunor suggests, discharging some of that stressful energy with hard physical exercise on a regular basis will help as well.
Another thing to consider is whether your dosage of Ritalin is sufficient. Perhaps you are getting used to your old dosage and a higher dosage might be more appropriate now. Or, perhaps you can take a slightly higher dosage on days when you expect those stressful work demons to attack.
Besides, some of us are just slower readers than others -- and it's tough to change that fact just because there's a room full of co-workers staring at us and expecting us to "perform" on cue. If you are normally a slow reader, requiring a bit of peace and quiet to digest the words on the page, it's ok to discuss that with your human resources office and with your boss -- you have the right to say that you'll be glad to read the document when the meeting is over.
Some of us ADDers can't juggle too many balls in the air at once. We may be able to pay attention at the meeting to what everyone else is saying, but that maxes out our attention capabilities, and asking us to read and evaluate a document while everyone is waiting for us to read, evaluate, formulate a response, and then deliver an intelligent sounding and relevant response is just asking too much.
I guess I'm saying that I would be responding like you -- I can read and process the written word just fine -- but not at the same time as I am asked to process the flowing discussions in a meeting.
--Rheanna