You can upload documents set against a property so that your clients can access them from their portal page.
Setting up a shared folder on a property
Go to a property, click on Documents > Add Folder > give the folder the name 'public' (all lower case)
You can click and drag any files you want to share regarding this property on to the folder or click on 'select files' and browse.
Customer portal access
View a client and click on View Portal in the Customer portal section. In the portal page they can click on the appropriate property where the shared folder is active.
To see the shared documents they can scroll down and click on the shared items under the Documents section.