There is no such capability native to Filemaker Pro.
Wow. So how do most people set up printing of documents from a portal? Just open each file and click print? Any workarounds?
You never know but that a plug in has something to offer. You'd need to do a web search for FileMaker plug ins to see.
It might be possible to use a command line or system script to print the document with FileMaker passing the needed filepath to the command line or system script. I don't know if that can be done, it would be OS specific (either mac or windows) and would depend on the default application set up to open the files of the types stored in your containers (word?, PDF? JPG? or ???) as to whether they could be controlled to print the documents via this method or not.