How to avoid let my boss do my work?

My boss is a PhD. When I am preparing a specification document,we have meeting with other groups again and again, because there is a lot of issues need to be agreed by all the groups. My boss is not full time there during the meeting, he usually half of the time there. Today he told me he want to help me to finalize the document, because I will leave for vocation soon. I am afraid he will mess up my document, because he is not 100% on those meetings, and he usually like to think and do things totally differently to other people. I don't want him to do my work, because this specification will send to our supplier. I don't want to spend more time later to fix the mess. So I told him directly I don't need anybody's help. I know he is unhappy about my altitude. What is the best way to deal with this kind of things.