My version of Contributae 3.1 and my client's version of Contribute 3.1 do
NOT allow us to overwrite a file according to these instructions (below)
from a Contribute Tech Note. We do NOT receive the dialog box that says

"What do you want to do ....1. Replace the file, 2. Publish your version
using a similar name"

It is important that we be able to upload a file and have it overwrite the
file with the same name already on the server.

"the user chooses File > Publish File From My Computer and browses to the
file that they wish to publish. Contribute then prompts the user to select
the website where the file will be published. If the file already exists on
the server, users can overwrite the existing file."