Many times we are asked to send identity document's copy, proof of payments, last phone/gas/electric bills, last paid invoices, last salary and so on, many times by e-mail, by whatsapp, by telegram...
How are these documents then going to be treated? Are they really disposed after? Are you sure that they are not going to be used for other purposes?
Though there is not so much that we can do to protect them, one very easy but effective trick is to add a watermark on top of them, so that if any misuse is going to be done anyone can pretend not to be adviced... :)
Just upload a photo of the document here above and have it watermarked as you wish; original documents are disposed immediately, watermarked ones are deleted after a week.