You can use dynamic text that references a field in the index layer. At 10.0 there is not a way to do this from the Insert menu. However you can add a piece of text and use the following syntax to reference an attribute field:
Also, at 10.1 we have added a Data Driven Page Attribute option to the Insert > Dynamic Text pull down menu, so this will be a lot easier in the future.
I just tested my 10.1 beta 2 to see how well it added an attribute field value and it's very nice. The only odd thing was the formatting defaulted to font size 5. Maybe that was just that instance but even if that was the default instead of formatting a text field ahead of time one would either do it afterwards, or copy and paste the expression into a pre-formatted text field.
The default font, font size, font color, etc. is taken from the Draw toolbar, so you can set this in advance and then any dyanmic text you add will be added with the font and size you want.
