Can I backup my Powerpoint and Word docs on iCloud

From a user perspective it is not possible to store any file on iCloud like on a usual drive. It depends on the applications if the use iCloud to store the files. Some apps like Apple's iWork suite for example can store files (Pages stores its documents, Keynote its presentations, Numbers its spreadsheets) on iCloud. In other words, if you find an app in the App Store which supports Microsoft's Power Point and also uses iCloud to save files, then yes. Just have a look in the App Store and search for apps in categories like "productivity".

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Yes you can do that.

You can add word, excel and PowerPoint documents to iCloud via the appropriate iWork application (ie, pages for word, numbers for excel etc) when you do this, they can be opened by iWork apps on mobile device or by iWork or MS Office on a computer.

In addition to this, you can add most types of documents to iCloud through text edit and preview.