If you are referring to a SWF export, you set the spread width in the export dialog in pixels. So something like Fit To: 984x588 would accommodate small displays—1024x768
However, keep in mind that SWF is basically a dying format: It will not work on mobile devices (tablets or smartphones), and many people no refuse to allow Flash plug-ins on desktop/laptop computers because of security issues. SWF is Flash.
refuse to allow Flash plug-ins on desktop/laptop computers
Although interestingly Google has decided to embed Flash into Chrome, which now has half the browser market. With Chrome there's no plugin to disable or update.