Hi @SandraSamper,
I'm not aware of a way to do this built into Canvas (or most other online systems to be honest). The way the web works in general if that if you're giving view rights, you're almost always giving download rights (as the web browser downloads things in the background to make them viewable). There are some scenarios where this is not the case, usually around video files, though sometimes PDF or other content as well, but there is nothing like that as far as I'm aware in Canvas.
I apologize, as this probably is not the answer you were hoping to get, but I hope it helps you to at least have this answer for now.
-Chris
