This blog post explains how Power Bi Admin can allow users with viewer access share their reports with others.
Power BI has 4 different levels of access with different options enabled and disabled.
When workspace admin assign a viewer access to user then user can see only the reports and features with in the report. User can’t share the report with other as the viewer access doesn’t allow user to see the share report option.
If user wants to get the share option on top of the viewer access then admin can enable the share option to the user. Follow the steps to enable the share option.
Check the below video to know details steps and what are all possible with viewer access with build permission.