Have used it for some months and it’s great. I mostly use it for basic stuff like splitting / merging pdfs because im too lazy to look up the pdftk command.
But there are many more features like sanitizing (removing embedded JS code) or OCR (which works great).
She certainly can’t break anything by using it, you can spin up a docker container and see for yourself. It’s also localized in a lot of languages.
I don’t think my own mother would do well with this, mainly because I think she doesn’t know what the difference between a pdf and word or libre doc is. But apart from that, it is really simple.