Password Protect PDF when user downloads

[eluser]jtkendall[/eluser]
I'm working on a project that involves the site admin uploading PDF's of his books through a CI based CMS I wrote, users purchase a copy of the book through the site, and then can download a copy. That's all very easy to do, however I would like to set the users email address as the password on the PDF. I know they do something similar over at http://pragprog.com/ (granted it's using Ruby).

Does anyone have a link to an article or an example of how to do this using only code that runs on your server? I did a quick Google search and found a few services that you can password protect files with their API, but I prefer not sending the files to a service every time a user downloads a copy. I'd rather it run on my server.

Thanks,

[eluser]pistolPete[/eluser]
How about those?

- http://www.idsecuritysuite.com/blog/pass...ent-in-php
- http://www.fpdf.org/en/script/script37.php
- http://www.pdflib.com/en/products/pdflib...omparison/

[eluser]jtkendall[/eluser]
Thanks, I'll give those a try.

[eluser]jtkendall[/eluser]
pistolPete, just wanted to say thanks once again. Option 1 worked perfectly!