Overview of PDF password protection: PDF security consists of 2 different passwords � a so-called 'user' password and 'owner' password. The first one can protect the document from opening, the second one can place restrictions to the document, for example print disabling. Used cryptoalgorithms were being improved with PDF developing � up to version 1.4 only 40-bit keys have been used, then the 128-bit ones came, and starting from version 1.6, AES encryption is being added.

However, PDF security system is implemented so that a file with restrictions may be decrypted instantly, irrespective of the password length, even for 128-bit keys. A document with password for opening, using 40-bit key, can be decrypted on a modern computer within a week by using guaranteed decryption. To open a document with 128-bit key, only brute force can be used.

File extensions: pdf
PDF crypto algorithms: RC4, MD5, AES (PDF 1.6+)
PDF encryption weakness: human factor, export regulations, stroring a key along with data
Possible attacks against PDF: brute-force, exhaustive key search
Attacks complexity: 2⁴⁰(PDF up to 1.4), 2¹²⁸(PDF 1.5+),

How can I recover PDF password? If you need to remove restrictions from PDF document then use the software that can do in instantly. If your document has password for opening and the key is 40 bit then use guaranteed recovery tools. Else, if key is 128 bit, please use the brute-force tool that has is optimized for your computer.

Guaranteed PDF Decrypter (GuaPDF) 2.3

(10641 downloads)

by PSW-soft

	: 12 days (40 bit key) / instantly (removing restrictions)
	: *3^ days (40 bit key) / instantly (removing restrictions)**
	: 9 days (40 bit key) / instantly (removing restrictions)
	: Pentium II/III; Pentium 4; Core 2; AMD; Dual

Demo
Price: $25.00

Description: The utility which allows you to instantly remove restrictions on PDF files, such as printing and editing (even with 128-bit key, Acrobat 7.x-8.x AES encryption and compressed files supported). It also can decrypt PDF files with password for opening (40 bit key only).

Advanced PDF Password Recovery (APDFPR) 4.0

(6397 downloads)

by ElcomSoft Co.Ltd.

	: 12 days (decryption, 40 bit key), 5000 p/s (128 bit key), instantly (restrictions removal)
	: *3^ days (decryption, 40 bit key), 12.000 p/s (128 bit key), instantly (restrictions removal)**
	: 9 days (decryption, 40 bit key), 8000 p/s (128 bit key), instantly (restrictions removal)
	: Pentium II/III; Pentium 4; AMD; Dual

Shareware
Price: $49.00

Description: A GUI utility to remove restrictions from PDF documents, such as printing, editing etc. Acrobat 3.x-8.x files supported. Pro version also allows to search for "owner" and/or "user" passwords with brute-force, dictionary attacks and has guaranteed decryption feature (for 40 bit key length). Enterprise version uses state-of-the-art "time-memory trade-off" technology, allowing to break "user" password in just a few minutes.

Elcomsoft Distributed Password Recovery 2.10.142

(9671 downloads)

by ElcomSoft Co.Ltd.

	: not tested
	: not tested
	: not tested
	: Pentium II/III; Pentium 4; AMD

Shareware
Price: $599.00

Description: High-performance distributed password recovery for forensic and government agencies, password recovery and data recovery services and corporations. Recover the most complex passwords and strong encryption keys in realistic timeframes. Accelerate the recovery by offloading calculations to NVIDIA GPUs and scale to over 10,000 workstations with zero scalability overhead.