How to password protect a particular Dropbox file so that only a customer can view it

You will need to login to dropbox.com and access your dropbox account via the web browser and then find the file in your dropbox that you want to share with the customer.  Once you have found the file then click on share.  You will then see a screen with the file you have selected and you can type in the customer's email address.  If you click on Link Settings then it will let you password protect the file for the customer.