To have Adobe Flash media in Preview I have a PDF document which has SWF file embedded (Adobe flash media).
Preview -program does not show it, but Adobe Reader shows it.

How can you have Adobe Flash in Preview?
You can't. Just use Adobe Reader if you have to view it.

You might be able to view it in Safari if you don't want to have to use Adobe Reader. Just right click on the .pdf file and select "Open With"