Acrobat files open as word files on website

I have built a website with hundreds of PDF files for viewing. This site has no word files on the server. Yet, when I click on a link to a pdf file, it displays first with the correct filename at the top of the acrobat screen, then displays a word file (.doc).; If I upload a new version of the pdf file, the previous version of the file is displayed, with the .doc extension. Again, there are NO word files on my server - not in the folder with the PDFs in it nor in any other folder on my site.

This makes absolutely no sense.