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Marc Hoffman, editor of OS Emulation, found that by opening an encrypted PDF in Preview he was able to re-save it as a new PDF but without the original security settings. What makes the issue more alarming is that when he created the PDF to test the problem, he disabled permissions to copy, print, change or extract data from the file. Nonetheless it was by selecting Print in Preview and then the Save

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As File option that allowed him to expose the shortcoming.

Hoffman passed his findings on to Kathi Rauth, senior product manager for Adobe, which dvelops the PDF format, and says that she assured him that Adobe and Apple had been discussing the issue for 'some time'.

It would seem that the problem lies not with PDF, but with Preview. 'Adobe has their security model as such that the secured PDF file trusts the program viewing it to follow certain guidelines,' said Rauth.

Her argument is emphasised by Adobe's PDF Reference files: 'Once the document has been opened and decrypted successfully, the viewer application has access to the entire contents of the document. ... It is up to the implementors of PDF viewer applications to respect the intent of the document creator by restricting user access to an encrypted PDF file according to the permissions contained in the file.'

Further details on Hoffman's findings can be found at PlanetPDF.