Yes it's a pdf
The network path is:
Z:\Supply Chain\_Acquisti\Contratti in essere\Fornitori Commerciali\2013
In this path the name of the file is: Contratto d'Acquisto - Parti Commerciali - 20130130 da firmare.pdf
If I upload it from a local path (i.e. my PC) or If I rename the document into "Prova.pdf" uploading works correctly.