All files are private in Saasuma: Only you will see them in the search results.
The one exception to this is where you have previously shared a file with someone in another product - for example in Dropbox - and where you want those sharing rights to be extended within Saasuma.
To set this up, from the Navigation Bar on your LHS, go to Sources
You will then see the screen below:
To allow users who have access to the content in, for example, Dropbox, also have access to the file in Saasuma, simply check the 'Inherit Sharing' box for that source.
If you do that, when a user runs a search in Saasuma, if the file you shared with them elsewhere is a relevant result, it will appear in their Saasuma results page for that search.