Files attached to Octopus data ("Attached files" tab in Incidents/SR, Problems, CI, Users, etc.) are all saved on your network, and not on the Octopus.

Their localization must be specified the following way: 

1. Determine at which location the Octopus attached files will be saved on the network. The location must be a shared folder on a file server, with an access permission so that all Octopus users (the support group) can read and write in that folder. 
2. Go to the menu "Tools > Options..." 
3. Find the sub-section called "Network directory containing the attached files", in the section "3 - Important general options" 
4. Enter the UNC path of the shared folder (\\myserver\OctopusAttachedFiles\)​

Octopus is now configured to save attached files in the specified path. Please note that there is no maximum number of files, nor a maximum size - the only limitation could you the available disk space on your server.