- Go to Share tab in your spreadsheet.
- Under Advanced options check the box to the left of Anyone can view this document at:.
- Copy and paste the URL that appears under this option, and distribute it to whomever you choose.
This means that their user names will appear in the Viewers section of the spreadsheet's Share tab, and they'll be able to see all changes made, in real time. Additionally, as with any viewer, they'll be able to copy and/or export this spreadsheet.