In MS Word, the Auto Recover feature automates the process of saving a document. In theory, this sounds great. However, as well as saving any changes to the document, it also retains any text that you’ve ‘deleted’ from a document.
This partly explains why documents that use fast save can bloat to very large file sizes. If you are concerned about deleted text remaining in your documents, you should perform the following steps:
Click File > Options.
Select the Save tab.
Clear the Save Autorecover information every check box.
See how to turn off this setting: