If you don't necessarily want the disclaimer to print at the bottom of the last page, you can put the disclaimer is a text box in the body of the report after the last tablix of the report design. If I were in your shoes I would experiment with both approaches to see which is the better look to the output.
I had a report requirement to print a "tear off" section at the bottom of the last page, and it had to fit pre-printed perforation, so I used the technique suggested above successfully. But if it doesn't have to be at the bottom, it might make more sense to print it after the last data region instead of forcing it to the bottom of the page.
It is always good to have options so that you can select the best approach for your design specifications.