PDF Security - a guide to securing your PDF documents

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PDF security


What is PDF security ?

Whilst PDF encryption is used to secure your PDF documents you may need to enforce other controls over the use of your documents.  In Adobe Acrobat a number of additional controls are proposed, such as printing, editing, copying, etc.

So PDF security is delivered by of a combination of different features - encryption, controls (digital rights management controls), etc.  - that are relevant to the overall controls you wish to achieve.

As we can see, PDF security can consist of the following components

PDF encryption
PDF digital rights management controls
PDF password protection or PKI
PDF copy protection

Now obviously the amount of actual security you achieve depends upon the strength of the controls you implement to enforce your requirements.  So underpinning any controls is the strength of the PDF encryption you have used.  If it is weak or can easily be subverted then any other controls are obviously going to be easy to remove or avoid.

PDF password protection has been the traditional way to impose PDF digital rights management controls on PDF document users, however as a method it has a number of drawbacks which are mentioned in the section on PDF password protection.

PDF copy protection is implemented through the use of PDF encryption.  It is almost impossible to prevent people from copying files – after all, everything on a computer has been copied in order to use it.  But if a file is encrypted , even if it is copied, if the recipient does not know what the decryption key is then they cannot use the file even though they have a copy.

PDF digital rights management is discussed in more detail at LockLizard's web site.

PDF security is achieved when the different components work together correctly.  So if some of the controls are implemented by one supplier and others by another you need to make sure that the combinations work together.

One problem in password based PDF security is that a number of suppliers provide tools for removing the protecting controls on the basis that you are the document owner and you have ‘forgotten’ how to use a document that is yours. Cracking by another name would be a crude misrepresentation.  However, reliance on some of the controls being provided may not be as wise at it seems.


Why would I want to secure my PDF documents?

There are many reasons why you would want to secure your PDF documents using PDF security.  The main reason however is that you need protection for your PDF documents beyond what encryption provides.  The most likely reason being is that you want to have some control of your PDF documents once they have been decrypted (for example whether a recipient can copy text from your document).  This may be because the information is privileged for a certain group of people or you are selling information that you do not want to be distributed at your cost.


So how can I secure my PDF documents?

Well, at the basic level you could use a product like Adobe Acrobat.  However it is wise to bear in mind that there are tools freely available on the Internet that remove the copy controls you have applied literally within seconds.

If you are serious about protecting your documents then you will probably want to purchase a PDF security product that uses US Government strength encryption (and is not password based – read PDF password protection to see why), digital rights management controls and does not use either passwords or plug-ins to secure your PDF documents.

We recommend Lizard Safeguard from LockLizard.  It is PDF document security software that gives you complete complete over your PDF files, preventing unauthorized copying, printing and distribution and will soon be available for sale on Ebay.

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