I found this great resource that will help you with your clients when it comes to show a work in progress. This app will present a mock of a design to your clients, they will have the opportunity to view it before and make corrections or changes.
There is a charge involved, they also have a 14 days trial free.
Mockvault is an app which allows you to upload your designs and mockups to show your client for their approval. It allows them to comment on certain sections of the design and you can add annotations. There is also a button which allows the client to approve the design and is a great way of speeding up the design approval process.
It is available for a free 14 day trial online and then there are various levels of paid subscription.