One biggest advantage of PDF is the ability to secure the document. So it is the most popular file format used for document distribution. Last time, I wrote an article mainly about PDF owner password, which can limit a user’s ability to copy text from a PDF document or even prevent a user from printing the PDF document. However owner password can be simply removed by PDF Password Remover . Today I will introduce another type of PDF password known as user password. You can secure your PDF files by set a password protection. Then others need a password to open it. It is vital for sharing sensitive information with only the intended recipients. However, sometimes, it happens that the creator of the PDF file forgets the password he used to protect. Then we need to crack PDF protection. It is not easy though.

Why is it so hard to crack open PDF password?
To crack PDF password at open level is a difficult and time-consuming thing to do. The difficulty of cracking the password relies on several factors:
1. The version of Adobe Acrobat used to create the file is one main factor. Lower version of Acrobat such as Acrobat 3.0 uses 40-bit RC4 encryption, which is easier to crack. But now with Acrobat 9, 256-bit AES encryption makes it much harder to remove. As for every password, there is much more possibilities added.

2. The complexity of Password is also important. Simple password is easy to crack, especially if it is the name of your child or the birthday of your wire. If the password was created at random with complex combination of upper case, lower case, numbers, and symbols, then it will be harder to remove.

3. The length of password is the last but not least factor to consider. Longer password definitely requires more time to try every possible password.

How to crack open PDF password?
The main methods to crack PDF open password are: dictionary attack, brute force.

A dictionary attack tries all the words in the dictionary. If the dictionary is larger, then you will have better chance of success. Generally, dictionary attacks succeed because many people have a tendency to choose passwords which are short. According to numerous researches, most people use passwords of up to 7 characters.

A Brute force attack is a method of defeating password by systematically trying every possible password. In theory, brute force attack will always be successful since the rules for acceptable passwords must be publicly known. But as the length of the password increases, so does the number of possible passwords. This method is unlikely to be practical when the password is too long.

There are several PDF password recovery programs available in the market. Most of them guess password with the methods mentioned above and optimized for speed. They will try to use all possible character combinations as the password and so it might take hours or even days to find the right password. You can try PDF Password Recovery. It’s affordable, and actually works.