I am not sure about SWF support in Acrobat 8.x, however, if it is supported, you will have to add it to the PDF after the PDF has been created. You can leave the space for it in your FrameMaker document and add it via the Mulimedia Tool.
I do know that SWF is fully supported in Acrobat 9.x, but in this case you will also have to add the SWF to the PDF after converting the FrameMaker document. To do this, marquee and area on the PDF using the Flash Tool; Tools > Multimedia > Flash Tool. You can also simply double click on the PDF with the Flash Tool. Support for SWF, and several other multimedia file types is much stronger in Acrobat 9.