Apps :: Word Document Corruption After Installation?

After installing Windows 10, I reopened some Word documents that have been an ongoing project for the past 8 years. They are long and complex documents including images, artwork and Chinese characters. I found that the formatting of these documents has been completely ruined! Everything has been moved around, some characters have been layered onto of one another and to top it off, the two fonts used for the entirety of the documents have been changed to another plainer font.

After checking the Word fonts, lots of them have disappeared, including the ones I use, and when I tried to import one of the old fonts in from a back up file, Word simply did not recognise it! Does Windows 10 automatically update to a newer version of Word when you install it? Is there any way to revert back to the way these documents were before the update? Manually reformatting them will take an estimated 1-2 years of work I tried looking at doing a system restore but there are no pre-saved restore points so haven't had any luck there, don't even know if it would work anyway..