The account's owner can export all the data in the account using the export function.
To export the account:
Go to the account settings
Click on "Data export" Tab
Click on "Export your account"
You will receive an email* with several attachments
Download all of the attachments in the received email
To get the account's data:
Make sure all of the downloaded files are in the same folder
Use a free app (For example Archiver) to extract your files: unpack ONLY the file with the "zip" file extension
Click on "extract"
Save the generated extracted folder of your exported account
*NOTE: It may take several hours for export data email to be generated and sent to your email.