Adobe CS4 is compatible with previous versions....

 
In Adobe Illustrator CS4 - Go to File > Save As > Format: Adobe Illustrator Document, then click Save Illustrator Options > Version: Illustrator CS3 (or CS2, CS1, CS, Illustrator 10, 9, 8, etc.) In Adobe InDesign CS4 - Go to File > Export > Format: Adobe InDesign Interchange, then click Save Adobe_Compatibility_files/designers_guide_transparency.pdf