If you have been using popular software all your documents will be readable in Linux. You will need to back-up your existing files so they can be replaced once Linux has been installed. It is possible to set up a system so you can boot into a choice of operating systems, but you will still need to back-up your data. Once Linux has booted you will be able to see your old data in a separate drive. Most of you files will stile be readable, however if you have been using specialist software, then you may be unlucky.
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