You can configure default item viewer settings. These settings are relevant when a link to a specific item or category is generated from the Content tab.  
For example, when a link is copied from the 'Get Item Link' page and pasted into Marketo, there are no predefined settings for how the item will be viewed. 

To configure default item viewer settings: 

1. Select the board for which you wish to configure default item viewer settings.  
2. Go to the Settings  tab > General > Default Item Viewer. 
3. Select the Item viewer type: Classic or Lightbox. 
4.  To allow downloading the item, enable the toggle. 

If you do not configure these settings, the default settings are lightbox viewer and downloading is not allowed.