Regardless of the version you are using (for Windows or for Mac) we recommend you to download and TEST free trial version before purchase. That’s the essence of shareware: you can try before you buy. The trial version can be downloaded from /products/flashoptimizer/ and will give you an idea of what can be achieved with your file.
The second step you should take if you cannot optimize well with Trial version is looking at your SWF file closer. Flash Optimizer shows you the detailed information about the SWF contents. Pay attention to the object groups which take the major part of your file.
If FO doesn’t seem to be doing its job
Either go through the tabs with settings and carefully play with the settings of the object type which comprises the largest percent of your SWF.
And you should always keep in mind that there are some SWF files which cannot be optimized at all like there are files which cannot be compressed with ZIP. If you were not able to get a satisfactory result with FO send your file to email@example.com for investigation and don’t forget to mention whether you are using Mac or Windows version.