Save the file path of the file (you don't even need to have it stored in a container) and use the Open URL script step to open it. Obviously the integrity of your document links are at the mercy, then of users calling the revised document the correct name.
If a file is inserted as a reference using the insert file method, it can still be opened via double click as long as the container field is optimized for images--not intractive use. A script can uses such a container field to open the file with Go to Field | Select contents. Thus, one trick it to hide an extra copy of your container field on a different layout without the interactive optimization and then use a script that uses that copy of the container field to open the file:
Go to Layout
Go to field
Go to layout [original layout]