I have two ideas that might possible help, though I don't think they will be perfect. Both only work for Word.
You could try the Abbreviation Management Package:
It is a plug-in for Word that seems to do what you want (I haven't tested it yet). It is not free, though: it costs $75. It has a trial version so you can see whether you like it. I have run it through virustotal.com and it appears to have no virus.
You could use footnotes in Word. When you hover over a footnote in Word, you see in a pop-up the text in the footnote: you can use this to display the meaning of an acronym. You need to create a footnote for an acronym, then automatically find & replace all instances of the acronym by acronym + footnote. You need to do this every time for each different acronym. It is not difficult to do, but it takes some time if you have many different acronyms. If you want to do this but can't get it to work, ask here. In order to do the process of creation and find-&-replace automatically based on a file with a list, you'd need to write a macro in Autohotkey or something. But that'd be some work.
If all you want to do is fill in all acronyms in a Word document once without the ability to expand/collapse (or pop-up), you could simply find & replace all the acronyms with their full meanings. I think it would be somewhat easier to write an Autohotkey script to do this automatically based on a list in a file. I am sure there will be people on the AHK forum willing to explain how this works and help you with the script.
Incidentally, I think this question rather belongs on Superuser.