In Flash CS3 when you did Modify/Document it allowed you to type in a document Title and Description which were metadata searchable by internet search engines. According to the book "Brilliant Flash CS4" this is still possible in CS4, but I think they have removed the option, and the book is wrong.
Is it still possible to add metadata for searching to FLA documents or is this now gone?
you can use metadata with cs4 but not the metadata tags that were added to html to aid search engines. the cs4 metadata tags are designed to smooth flex/flash work-flow.
i believe, html metadata tags are now of minor importance to search engines. but if you want to add them using cs4, i believe you'll need to add them by hand.