Document modified in iCloud

I’ve spent a good deal of time on the phone to apple support and she suggested I reach out to the apple development team, however i don’t have a developers account so can’t access their support forums.

I created a document in iCloud, on my Mac book, I created this document from scratch, put a password code, and locked the windows. And exited iCloud from my Mac each time I had finished. I first noticed it had been modified (I also look at date of when document was modified data)1 or 2 days after creation, so I restored the document back to what I saw I had inputted.

I did share said document to an email, the recipient doesn’t have an apple account, so didn’t access their document, and I revoked the share ability 2 days ago.

i went into said document today, and data has again been removed, modified, yet I haven’t accessed the document at all. I’ve reset my account passwords, I’ve erased my Mac book and reinstalled the system today.

unfortunately the lovely customer services team were unable to advise me on how to keep my documents safe. And while the document details are important, I have the originals in paper form, I’m more concerned that my documents are been accessed and modified without permission. And I have most likely missed an important detail above, if an apple developer could be assist me, I would greatly appreciate it.