Technical Documentation

I have been engaged by a civil engineering firm to develop a blue print for a paper less office environment. I have started end user analysis & understanding of as-is system. Till now most of the employees have told me that CAD files, used extensively in the firm, are a major hurdle in complete electronization of all office procedures.I need some advice/help in developing the concept for the to-be system & where I can find more information on writing technical documentation viz installation manuals, user guides etc.