Converter for Keynote is an app that allows you to quickly and easily convert Keynote 4.x (iWork 2008) files to Keynote 5.x (Keynote 2009) You can then open your old Keynote presentations in the latest version of Keynote / iWork. This avoids the dreaded "This presentation can't be opened because it is too old" error. Without "Converter for Keynote" you will need to have a Keynote '09 installed to do this. This useful and easy to use utility stops you having to buy or install iWork '09 just for this simple task. It even allows you to batch-convert Keynote '08 files to Keynote '09. It's the only converter that allows you to migrate all your documents in one go...!
Updated on Mar 22 2016
Note: Now requires OS X 10.9 or later