You can unlock protected PDF files using some programs that are designed to remove password from protected PDF files. However, there might be occasions where you may also want to recover the lost PDF file password and not just unlock the file by disabling its password.
In this post we are introducing you to some good PDF password recovery tools that you can make use of to recover forgotten PDF file passwords.
Common Password Recovery Methods
A PDF file typically has two types of passwords – The User and Owner Passwords
- User Password – Used to prevent people from opening or viewing a PDF file
- Owner Password – Used to prevent people from printing, copying, editing, adding or deleting pages from a PDF file.
Most password recovery programs use Brute-Force Attack, Dictionary Attack and Mask Attack methods to recover lost PDF file passwords.
Dictionary Attack – Mostly passwords are based on words and phrases. Hence, this method is based on trying out different combinations of words, phrases and characters available in a specially maintained dictionary.
This dictionary is constantly updated and contains all the previously searched words, phrases and characters used in passwords.
Brute-Force Attack – In case the Dictionary method fails, the Brute Force method tries out all possible word and character combinations by using the Brute Force method until it finds the right password.
Although it sounds cool, Brute Force is the most inefficient and dumb way to recover passwords. A simple nine digit password (johny1988) using a name and date of birth combination may end up using billions of trial and errors before it is cracked.
In case you are interested, it is possible to come up with 472,161,363,286,557,000 possible password combinations, using just your 5 digit first name and the year of birth.
Calculation: 2 x 26 lower and upper case letters plus 10 numerals=62. Since the password is nine characters long you will be able to come up with 62^9 possible ways to arrange 26 upper case letters, 26 lower case letters and 10 numerals (1 to 9 and 0) in about 10 years!
Mask Attack – This is another password recovery method that aims to shorten the password recovery time by using common knowledge about human nature and how most people design passwords.
Recover Lost PDF File Password
Now that you have taken a look at some of the most common password recovery methods, let us take a look at some reliable password recovery programs and tools that you can make use of to recover lost or forgotten PDF file passwords.
PDFCrack is a true PDF password recovery program, it can recover both User and Owner passwords. The program is known to work for files with 128-bit RC4 encryption.
This tool is really easy to use – just upload the file from your computer and hit the crack button. You can find this tool at pdfcrack.com
PDF Password Recovery
This is basically a paid tool that you need to purchase for $29. There is a free Demo version of this program that recovers and shows you only the first three characters of the User password.
The ‘Stellar PDF Password Recovery’ is a powerful program that uses Brute Force and Dictionary recovery methods to recover lost PDF file passwords.
In Brute-Force method the program creates all possible combinations of characters and recovers the password. Dictionary Attack uses an algorithm to search for the password in a specially maintained dictionary that contains all the previously searched passwords and possible values for the password being searched.
You can access this program at stellarinfo.com
Jihosoft PDF Password Recovery
Another paid password recovery tool that can recover both user and owner passwords. This program uses Brute Force, Dictionary and Mask attack methods to recover lost passwords.
You can access this paid password recovery tool at jihosoft.com
Important: You should never try to guess or recover passwords for files that you do not own and that have been protected for a reason.
Above information is intended to help regular users who may have lost, misplaced or forgotten passwords for their own Protected PDF files.