After the internal error of Ellipsus in the morning, I want to share some tips for storing your documents:
Always have a backup: Every time you end a chapter, make several changes or just need a backup download it as .md file. PDF is uneditable, but markdown can be used to restore docs if lost (and can be used in programs like Obsidian)
Use physical storage: USB, DVD, print and use a simple bind, whatever it works with you. Your PC can shut down and you lose your files, and if there comes the end of civilization you have the printed version. Just keep it away from other catastrophic events.
Do NOT have everything in a single place: I use several hard drives and apps to store my data. I print and bind things I'm proud of. I make time clauses on my USB. I copy important data on Fortelling. I put my .ebup files on my e-reader.
If you think I'm being paranoid, ask yourself: Can I be the next one with a bit of bad luck?
So, just in case, backup everything you can.
Even emailing your files to a friend can store them better than nothing!!!