Adding Furigana to ENTIRE Document?

Japanese Language Questions
1

Not super hopeful but I have to try: does anyone know how to add Furigana to an ENTIRE DOCUMENT all at once? I am a highschool teacher, and I need to add a LOT of Furigana to an essay reading I’m assigning; however, as you might know, Word only lets you add Furigana in small chunks.

Apparently at one time there was a Google Docs add-on that let you do this, but that appears to be either discontinued or broken. I’m down to use whatever program or whatever add-on, I just really don’t want to do all this friggin Furigana manually…
ありがとうございます！

2

僕も知りたいです。助けてください！

3

could this work for you?

4

助たすけて下ください。信しんじて

Oh, hey. It does copy properly here.

5

Hey, not bad.
神の真の心
Would’ve been
しんのまのしん
In Microsoft word. But this to got it all correct.

6

Ohhh hey this is the most promising thing I’ve seen yet!! My laptop stopped working this morning of course so I can’t test it but I’m hopeful! ありがとうございました！