Well, since swf files are Flash files you would probably be better off asking this question in the Flash forum. Also, you should get the original .fla files to edit...there are decompilers for Flash that will allow you to edit swf files but I would be concerned that whoever wants the editing done might not have the rights to the work if all they have are swf files.
I will ask in the Flash forum. I working on my client's website, so I will ask them if they have the files or if they can get the files. Thanks for the responses!!