Short answer
You can download individual documents from an Index by using the download option in the document review screen.
Full explanation
AskTuring does not currently provide a bulk export option for all documents or data in an Index. However, you can download individual files as needed.
To download a document:
Go to the Files screen in AskTuring.
Click on the document you want to download. This will open it in the document review screen.
Use the Download button in the upper right corner to save the file to your device.
AskTuring recommends keeping your own local copies of files you upload, especially if you plan to delete them from the Index later.