[masswerk]

> "iCloud secures your information by encrypting it when it's in transit and storing it in iCloud in an encrypted format. Many Apple services use end-to-end encryption, which means that only you can access your information, and only on trusted devices where you’re signed in with your Apple ID."

https://support.apple.com/en-us/HT202303

Edit: Mind that this would still apply much the same to copy-and-paste in MS Word and any (encrypted) remote backups of the resulting documents. Where is the significant difference? Also mind that iCloud backups are not mandatory, but yet another (optional) service.

[e44858]

> Many Apple services use end-to-end encryption

Not all. Notably not iCloud backups. They're encrypted but Apple has the key.