How do I display long list of client on a page using keynote
I hope I unterstood what you want...

I tried to create an example: scroll_example.zip

Follow these steps:


Create all your client names
Group them all to one object (if they're all in one textbox, skip this step)
Create an action for that object -> Move
Set the action from bottom to top and specify the duration
Place your object outside your slide and end position of the move action is of course in your slide (see the example)