Heaven forbid I should steer you away from an e-ink device, Yvan... but I think maybe it might not be the best way to do those business things. It may be a pain to keep all the right docs on it, and to navigate to them. Your clients would lose interest by the time you got to the next drawing or contract. And the screen is probably a bit smaller than you might want.
It's really awesome for reading a novel from front to back, but for random and frequent navigation across documents and pages, the e-ink is just too slow, in my opinion.
A UMPC or small laptop or small tablet would seem to be pretty good for those kinds of activities, and would be a lot of fun when you are not with clients also!
But much more expensive.
Alas, so far there is no great universal solution for computing and presenting and reading etc etc.