how to make the contents of a file disappear after x numbers of days or at date

[Alan Pope]

On 9 September 2010 19:03, user1 <bqz69 at telia.com> wrote:
> Lets say I want to send a picture to a person - then I do not want the
> person to copy it and use it for "some purpose" - the person is not an
> expert, so after a day in his posession the contents of the image
> disappears - same idea with a text file?
>

You're basically describing DRM, nothing more.

http://en.wikipedia.org/wiki/Digital_rights_management

Examples of which:-

http://www.fileopen.com/products/fileopen_pdf_control/
http://www.locklizard.com/pdf_security.htm

I'll let others pass comment on the morality and effectiveness of such
an idea :)

Cheers,
Al.