Edit pages in a Sandbox mode that does not affect the live site. Send clients a special link to view the Sandbox mode version of the page. Push to live site when ready.

See:

-Hydrogen's Sandbox mode for Oxygen: https://www.cleanplugins.com/products/hydrogen-pack/#feature-sandbox-mode

-Wakaloka Sandbox (dPlugins): https://dplugins.com/products/sandbox/