I have created a pdf voucher/card to send to specific users, they store it on their phone and display it to get a concession. But it has occurred to me that they could pass on the pdf to others.

Is there an app or method which would allow me to send/install a document on a device that can not be shared.


You can do any of:

  • Write a mobile App for at least Android & iOS to display the content of a custom or encrypted file format, (possibly having used some identifying features of the phone as the key).
  • Send an encrypted PDF file requiring a key to unlock it - a favourite trick that I have come across is to use the purchase credit card number as the key on the grounds that people are unlikely to share that.
  • You can make it harder to share by encrypting with a certificate (average users will know how to find the PDF but fewer will know how to find and identify the certificate.
  • Customise the PDF with the end users Name, possibly photo, and Mobile Number - this will allow verification of the individual presenting the voucher at the time of presentation and at least give the recipient a little pause before sharing as they will know that they are traceable.

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