When you add someone to one of your files as a Viewer, they will be able to access your file without using up any of your Cloud Credits. Viewers do not need a Wolfram Cloud product subscription.
Each subscription plan includes a set number of free Viewers. This number is tied to your account, not individual files. For example, Home includes five free Viewers, but you can add each of those Viewers to an unlimited number of files.
You can also share your files with as many Wolfram Cloud product subscribers as you like.
When you give people Viewer access to a file, they can view and interact with it, but they won’t have the ability to edit it. In order to edit the file, individuals must be added as Collaborators.