This program is designed to work on plain text (.txt) or HTML files. The program will process other file types, but the results will be wrong, so if you have something like a Word document, save the file as plain text first.
This program does some serious number-crunching, which can take a while if you have a large file. If you're uploading your PhD thesis, you might want to make dinner while you wait for the results.
If you found this program useful, you might also be interested in our concordancing program.