You can always prefix any CSS with .page-id-XX (where XX represents the page ID number assigned by WordPress).
Finding the correct element in Firebug or Chrome's Inspection Tool should result in the ability to apply a padding-left or margin-left. I'm doubtful that float:left will work as it would probably cause a conflict with the button.
To answer your query about a box for a Callout Section, such a class would be applied to the whole Callout, which is a pre-styled section with a particular layout. As it wouldn't apply to any individual component of the Callout, there would be no impact on redesigning its layout. This is why direct, custom CSS is a more effective, efficient and productive method of customization.