I store it in paperless. I save it there for the longterm but also to have it ready when needed. If I guess I don't have internet. I save it on my phone as well.

I print hard copies because (a) I'm a dinosaur (b) it's easier than fumbling with a phone

I put them in my password safe

pdf in my nextcloud

I'm almost 100% paperless nowadays, which I achieve using (heh!) Paperless-ngx.

So far, the best FOSS Android app I've found to go with it is Paperless Mobile. It's pretty well featured, and is being actively developed.

Save them as PDFs and store them in your cloud storage or choice or a syncing tool like Syncthing. A basic folder structure can help keep things organised.

No need for anything complicated, for essential documents best to keep its impel and limit the scope of failure.

Like most others I use paperless-ngx.

On top of that, I use syncthing to sync the paperless files to my mobile phone. You can set storage path for each file in paperless; I have one for important files like tickets. Then I have them even without internet access 🙂👍

I also use email and company apps (flights, ..) .. 🫣 For movies I also use "note to self" in signal to quickly store and find them..