Can I scroll the display on an STU?

STU signature pads are essentially "dumb" terminals and do not have any in-built scrolling capability - they simply display images which are uploaded to them.
It is possible to simulate scrolling by providing the user with control buttons such as arrow keys to move between different screen displays.
A very basic sample for this is provided in WizardScript-ScrollBar.html in the Signature SDK Extra HTML Samples on GitHub.

Please note that the uploading of an image to the STU always involves a certain amount of delay, depending on various factors.
In particular colour images take significantly longer to upload than monochrome ones.
Therefore the provision of scrolling via a mechanism such as that demonstrated in the above-mentioned sample may turn out to be impractical.
In most cases it is probably better to spread the text over consecutive screen displays using standard Next and Previous wizard-style buttons.