You can open any application by using "Send Event" FileMaker script step. By this "Send Event" step you can execute any dos/shell command or any batch file even. Follow below steps to use the "Send Event" script step.
For FileMaker Windows: select Send Event script step -> select Send the open document/application -> in Text wirte "winword.exe"
For FileMaker Mac: select Send Event script step -> select Send the open document -> in Text wirte "Microsoft Word.app"
add this script step to any script and attach that script with a button.
You can also use Insert File with the "store a reference" option to insert a reference to the document into a container field. You can then double click the container field to open the file.
Note: if you are using FileMaker 12, this will not work if you "optimize" the container field for interactive content on the layout where you want to double click the file.
brilliant thanks alot :-)