I believe you need to use tableau server or tableau online for this:

Tableau Online Tip of the Week: Using tabcmd to send emails

In terms of licensing, if you're sending workbooks/dashboards/whatever to "non-users" (meaning they don't have a Tableau license ?) then you're breaking the rules of the license agreement.

Once your leadership team have an individual login, you can subscribe them to a dashboard so they can click to login to Tableau and see their stats.

Even if they just want the PDF, much easier to comply with the license and set them up as individual users.

You can manually share PDFs. You can even share workbooks for free or with the lower cost viewer license. Learn more about Reader or Viewer. They would need to be some form of licensed users to be subscribed and automatically receive emails with images of vizzes. But there a couple ideas in the forums for Subscribing to PDF that can be voted on here and here.