Unless you have an articulable reason for using the 64-bit version of Office, you should be using the 32-bit version. Having a 64-bit operating system is not such a reason. There are known compatibility problems with the 64-bit version of Office. There are no known benefits to using Word as a 64-bit application. Some very large and complex Excel spreadsheets run better in the 64-bit version. As far as I know, it is all or nothing as far as Office version goes.

That doesn't address your question, though. It depends on what you mean by uneditable. A basic rule is that anything that can be seen can be copied. Anything that can be copied can be edited. All you can do is make it harder.

An easy way to make it harder to edit a text file that can be searched is to convert it to a searchable pdf and apply protection to the pdf. This requires Acrobat or a similar strength pdf generator.