You can export all of the documents used throughout the sales process (subject to your access privileges) in the 'Case export' tool.
To access this, click 'View' on your chosen development, and then 'View' next to the relevant unit.
Above the stakeholders in the top right you will see a 'Menu' button, click here to display the 'Menu' sidebar and click 'Case export'.
Here you'll see a list of the documents you can download. Simply click 'Create Case' and the portal will package up all the details into a ZIP file ready for you to download.