I have produced a document in pdf format that will be sold from a website.
Is there any way to restrict distribution of this. I have Acrobat 7
and know how to prevent printing and/or editing but I would like to
prevent customers from sending the document to their
friends/colleagues. Perhaps there is a way to allow one copy to be
printed and then the file can not be opened again? - Or is there
another solution?

http://www.docurights.com/demo.html 
http://www.docurights.com/(you can use docurights) 

you can also use Adobe Acrobat Reader to protect the copyright of your pdf files
 Security 
 Security settings
 Digital Signatures
 
 My Digital Editions

hope this will help you a little bit.

http://www.verypdf.com/encryptpdf/protect-pdf-tool.html

this tool also has an Owner Pasword and User password.

http://www.verypdf.com/encryptpdf/protect-pdf-tool.html

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