Digital fingerprinting in PDF files

[workerbee]

I have a question for those among you with PDF expertise.

I subscribe to the PDF edition of a magazine and have thought about uploading the issues to TPB. Although I see nothing suspicious in Adobe Acrobat's "Document Properties" dialog box when the file is opened, I'm concerned that the issues may be otherwise tagged by the publisher with an embedded digital "fingerprint" that could be traced back and identify me as the uploader.

Does anyone know how widespread the practice is or how I could determine my vulnerability? How can you tell if a file is so tagged?

[Kingfish]

You can remove the metadata from a PDF and you should do so.

[The_Abee]

Yes! Remove the metadata & make sure to delete the certificates associate with the book as well. In Below image I've marked a demo highlights, I'll advice you to do the same. Though in that case creative commons are not any problem to share but others are.

[WDoubleYouW]

I would simply open the PDF in Google Chrome and Print to PDF. That strips all file protection out of the file if any as well.

[workerbee]

Thanks, Abee. You can see in the image below that, unlike your sample, my file doesn't show any URL in the Advanced Properties. Does that mean I'm in the clear? I assume the other information shown -- the XMP Core and Media Management Properties, Dublin Properties, and PDF Properties -- does not pose any problem, is that correct?

[Bozobub]

I would not make that assumption.

I'd follow the above advice and run it through Chrome or a more-specialized DRM-removal app. before any distribution, for starters. Remember, this IS The Pirate bay, you can find 'em here, but there are several legally-free tools that may be a better idea. That "OriginalDocumentID", for example, troubles me a good deal.

Also, I'm definitely NOT saying that it's present here, but digital watermarking can also involve logos or coding in images in the main body of the text, since it's a PDF. If not visible, it's just a steganographic code IN the image (which also does not preclude a visible "real" watermark, as well). So far as I've seen to date, this type of steganographic watermarking is only common in very limited publishing fields (textbooks, especially), so your magazine is likely to be mostly clean, but keep this in mind; I imagine it will only become more common, as it's cheap and can be moderately effective for finding the initial vector of a publication's release.

[workerbee]

You've got a really good eye, Bozobub. Thank you for pointing that out. The Document ID numbers under XMP Media Management Properties are indeed troubling. They couldn't be deleted within Acrobat but running the file through Google Chrome seemed to strip them away very nicely, as the image below indicates. Thank you for pointing out that trick, WDoubleYouW!

Do you recommend that I use DRM-removal software in addition to Chrome? I'm a complete novice when it comes to these things. Can you recommend one or more good packages for use on a Mac? All the software that I see appears to be dedicated to removing DRM protection in audio files. Would it also handle non-audio files like PDFs?

Thank you all for your helpful responses!

[ViperScale]

You can do batch job on a folder and remove all the meta data etc from there using adobe pro.

[The_Abee]

@workerbee Yes! in your sample no certificates are associated with the book. That's why you can't see any. And, off course Opening a PDF in Chrome & then print it as PDF is quite easy & rather time saving trick but It has a problem. It decreases the interactivity of the PDF e.g. All the link* would be gone too (with metadata) & PDF would lost it's effect. That's why I didn't recommend it first.

And, as far as it concern to "Digital Watermarking" than I really don't think even Chrome technique can remove that. Coz, Digital Watermarking is 'entered' into audio, pictures, video, texts or 3D models etc. Not particularly in PDF so, that watermarked info would stay there in 'object' itself even after Chrome technique. But "more-specialized DRM-removal app" can definitely help & can make the PDF secure to 'share' without any doubt. Even tell me as well the best to use "more-specialized DRM-removal app" that you'll choose.

* I'm not talking about Web Links but the Links within document. Like those in content list etc.