What do you mean "brought back"?
You're not expecting to open some ancient EPS or flattened PDF and be able to fully edit it?
Save in AI format or at least AI compatible and have an editable file.
By brought back, I mean re-open. Save and close, then re-open. These aren't ancient EPS or flattened PDF; they are newly created in CS4.
Then what exactly do you do? And what exactly do you save? Even in CS4 you can create files in ancient formats.
Don't save as .pdf if you don't want .pdf.
Illie isn't a pdf editor