You can invite a client to sign-up to DesignFiles one of two ways...
1. You can invite your clients to fill out a questionnaire which would automatically register them as a client for you on DesignFiles when they submit it.
You can send the questionnaire link to your client directly or use the invite via email option in the invitation tab :)
Here is a detailed list of the various ways to Invite a Client to Request a Project
2. You can invite your client to sign-up by sending them a design or a document through DesignFiles. This will also automatically request them to register for a client account if they are not already registered.
Here are the steps to Inviting a client to review a design