Users can simply copy and paste the generated link for the selected document using this option when required to be sent outside the Dynamics 365 CRM.
If only View is selected then the document is available in read only mode whereas, if Edit mode is selected then the document is available for editing. For Dropbox, only View mode is available. This feature is also available in Azure Blob Storage.
However, if you get an error while creating an anonymous link, then follow the instructions given here.