Google has downgraded Gmail so that it no longer cracks PDFs with the no-copy-bit set.
Gmail has crippled its "View as HTML" functionality so as to comply with Adobe's PDF copy-control scheme. In case an email attachment is a DRMed PDF file (= a PDF with copying and/or printing restrictions), clicking on the "View as HTML" link returns the message displayed in the screenshot.
(Thanks, Andreas!)
Update: Perrin sez, "Adobe's own Macromedia Flashpaper 2, will convert a DRM-ed PDF into a PDF with all the DRM stripped. I just tried it on an ebook I purchased from Amazon and it worked flawlessly."
