Discussing a text based document with a client not sitting your office is, to say the least, inefficient. It is very difficult to be sure that everyone is looking at the same thing and when the document is a blue print or diagram it would seem to compound the difficulty. I got this question from a lawyer in the latter situation.
Real time computer screen sharing and annotation is one great way around the problem. Acrobat Connect, which is part of Acrobat.com, is an excellent service that allows anyone on any type of computer to collaborate very effectively with a range of meeting room tools; for free.
The video here is a quick overview of sharing a file with another person so everyone can see the exact same thing at the exact the same time. Acrobat.com has a number of great features worth a closer look including an online word processor. Acrobat.com works very well with Acrobat 9.