This refers to a technique used to prevent copying of PDF files by both authorized and unauthorized users. However, whilst it is impossible to stop users from copying PDF files, that does not mean that you can’t stop users from using them by applying PDF file protection. Therefore, the most viable option to PDF copy protect a document is by ensuring that one cannot access the PDF file without authorization. Let us look at how this can be achieved.
A PDF lock is an effective access control method used for limiting access to pdf documents. There are many ways that one can use to implement this access control like the use of passwords and registration codes. Other types of PDF lock can be achieved through hardware (a dongle) which has to be present to open the lock. For effective PDF file protection, a lock using encryption is necessary to prevent anyone from accessing a PDF file without a suitable key.
When implementing a PDF copy protect product there are different locks that one can use to prevent unauthorized access. A simple PDF lock only requires a password to allow access to the protected document. However, http://www.newsoftwares.net/copy-protect/howto/ this is not a very effective lock as passwords are easily given away or are sometimes compromised with password attack tools. Other files include passwords within the document therefore compromising them.
A thorough PDF file protection system uses license controls independently of the lock being used so that protected PDF documents can only be opened on specific computers that have been authorized. If the computer is authorized then the decryption key can be obtained and the document can be opened. This PDF lock is more complicated to pick. However, a secure lock must also have the capability to stop authorized users from passing on information once the document is unlocked, and this can be implemented using DRM controls.
In conclusion, it is beyond doubt that a good PDF copy protect product cannot be used to prevent people from copying physical files. Copy protection is obtained by ensuring that the copied files are of no use unless the user or computer has been authorized. The main factor here is to ensure that the cryptographic key for decrypting these files cannot be passed on to others. This can achieved by making sure that the decryption key is protected and locked to individual computers. This is a very critical feature required of any credible PDF copy protect product available in the market.