I use Invision quite a lot. If you don't know about it, it's an online design collaboration tool for sharing and commenting on design layouts.

Live Sharing has recently been added, but it's crazy good. As I design a PSD (or Sketch), I save the file to the Invision Live Sync folder, which is like Dropbox. Invision automatically creates a jpg from that and uploads it for commenting and mods.

Invision is also pretty awesome in that it keeps also a history of design edits. So each save is then progressively added to the history, kinda like a design time-machine.

if you're a freelance designer, Invision is a key tool - along with Marvel and Slack.

Just a heads up.