Check out this thread: https://community.powerbi.com/t5/Desktop/Hide-Pages-Based-on-Roles/td-p/110322
Currently there isn't an option to to hide the pages.
Right click on the tab to hide the page, then a green checkmark appears, indicating it's now hidden. Simply do the same thing to get rid of the checkmark to unhide. It won't say "Unhide Page" after its been hidden, in other words. The checkmark is used to indicate that the page is hidden, as well as the font color change on the tab name.
Ah - that could be it. The Power BI with Reporting Server is a different download than Power BI Desktop I'm referring to.
The download with reporting server may not have the same capabilities, including the ability to hide tabs? (Again, I cannot confirm this since I do not have reporting server downloaded.)