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Digital Rights Management for PDF Files & Documents
What is PDF Digital Rights Management (PDF DRM)?
Although Adobe might like the mantle of having invented digital rights management for documents, there is no effective evidence to support that suggestion. However, it would be correct to point out that that the general adoption of the PDF format as a common presentation across multiple platforms has catapulted the Adobe approach to controls being those that are generally accepted as the default situation.
So what are these 'default' controls?
Well, the initial controls were:
- no printing
- changing the document
- copying or extraction, Disable accessibility
- no adding or changing comments or form fields.
These were later augmented to:
- printing – fully allowed, low resolution, not allowed
- allow content copying and extraction
- enable content access for the visually impaired
- allow only document assembly *
- allow only form field filling or signing *
- comment authoring field fill-in or signing *
- general editing, form field fill-in or signing *.
* these choices are mutually exclusive.
And then refined into:
- changing the document
- document assembly
- content copying or extraction
- content extraction for accessibility
- filling of form fields
- creation of template pages.
And one must not forget the control of watermarking, either on-screen or on printed output, or both.
So, a great many of what are considered to be DRM controls may be seen as PDF digital rights management because they are the controls that Adobe found appropriate to provide when they developed their own approach to portable document management over a great many years. It has to be said that these may not reflect the same type of document rights as are envisaged by groups such as XrML, but the Adobe ones have been implemented on a global scale, and have stuck, which is more than can be said for the rest.
The core DRM functions in PDF digital rights management are printing, copying/extraction and changing with save. This is because it doesn't matter what kind of publisher you are and what you are trying to achieve, you are going to need these functions whilst the work remains in Copyright.
Watermarking as a PDF DRM technique is, to be strict, a bit of an open question. On the one hand, many publishers wish to be able to allow their customers to make printed copies of information, but on the other they recognize that converting a good printed copy of a book into (say) a PDF format is trivial. But putting a heavy watermark on a document detracts from the visual quality of the result, and a light mark may be removed by adjusting scanning contrast. The same goes for attempts to watermark pictures. Some systems even try to put watermarks in that 'identify' the purchaser, to help prevent purchased copies from wandering. The jury remains out as to the actual value of watermarks in DRM, but they seem here to stay in the video and broadcast businesses, at least.
The PDF digital rights management of assembly, filling in forms, comment authoring, signing and templates are particular to facilities that Adobe specifically included in their products which are focused around document collaboration. Most of these are not likely to find their way into commercial publishing initiatives, although they may be appropriate in the elearning or education at a distance markets.
Finally we consider controls over document accessibility. This may well be one of the most vexed of the Adobe proposed PDF Digital Rights Management controls. Some cite Adobe Systems' release in 2000 of a public domain work, Lewis Carroll's Alice in Wonderland, with DRM controls asserting that " this book cannot be read aloud" and so disabling use of the text-to-speech feature normally available in Adobe's eBook Reader as a perfect example of DRM overreach. Certainly, if a person with poor sight purchases a document that can be 'spoken' from the word text, is it right to prevent them from being able to use the document in that way? I don't know any safe way to turn the famous Tenniel illustrations into words, but that would not stop plenty of Jabberwockies from having a damn good try. Given the stance of many governments, led by the European Union and Canada, into providing accessiblity, artifical restrictions on accessiblity may prove politically unsound.
So there you have it. PDF digital rights management controls represent a well thought out series of controls. We can argue about whether they are complete, appropriate or suitable. But they represent a significant stake in the ground about the controls that should be applied. In analysis, you can break PDF DRM controls down into three groups, those for pure publishers, extensions for additional control and those for document collaboration. Sometimes these distinctions may blur, but they have stood the test of time as being useful.
Are PDF Digital Rights Management controls effective?
It is important to understand the difference between providing PDF rights management controls and them being effective.
In many instances proposed PDF rights management controls have been so poorly implemented (see PDF password protection) that you have been able to drive the proverbial coach and horses through them. Indeed there are some web sites who offer what appear to be tools dedicated to the cracking of much of the Adobe implementation. Not suprisingly, third party vendors have moved to providing controls that are less open to many of the attacks that have been popularized by such companies as Elcomsoft. See PDF Security Issues, Flaws and Cracks for articles relating to these attacks.
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