Overview of PDF password protection: PDF security consists of 2 different passwords: a document open password and permissions password. The first one can protect the document from opening, the second one can set restrictions to the document, for example print disabling. Used cryptalgorithms 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. In the latest Acobat 9 version AES keys were extended to the 256-bit length.

However, PDF security system is implemented so that a file with restrictions may be decrypted instantly, irrespective of the password length, even for 128 or 256-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 or 256-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+), 2^{256 (PDF 1.7+)

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 is optimized for your computer.}

Parallel Passsword Recovery (PDF module) 1.5

(868 downloads)

by Parallel Password Recovery

	: not tested
	: *130.000^ (128-bit) / 2.000.000^* (256-bit)**
	: not tested
	: 600.000 (128-bit) / 80.000.000 (256-bit)
	: Pentium II/III; Pentium 4; Core 2; AMD; Dual; NVIDIA GPU

Commercial
Price: $29.00

Description: The utility to recover PDF documents open passwords, 128 and 256-bit RC4 and AES encryption supported. Supports all Acrobat versions up to 9.0. Effectively uses up to 8 CPUs and NVIDIA GPUs. Contains special Password Definition Language.

Guaranteed PDF Decrypter (GuaPDF) 3.1

(14723 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)
	: 1 day
	: Pentium II/III; Pentium 4; Core 2; AMD; Dual; NVIDIA GPU

Demo
Price: $25.00

Description: The utility which allows you to instantly remove restrictions on PDF files, such as printing and editing (even with 256-bit key, Acrobat 7.x-9.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) 5.03

(8720 downloads)

by ElcomSoft Co.Ltd.

	: 12 days (decryption, 40 bit key), 5000 p/s (128 bit key), instantly (restrictions removal)
	: *3^ days (40 bit key), 14.000 (128 bit key), 2.300.000 ^* (256-bit key) / instantly (restrictions removal)**
	: 9 days (decryption, 40 bit key), 8000 p/s (128 bit key), instantly (restrictions removal)
	: 18.000.000 (256 bit key only)
	: Pentium II/III; Pentium 4; Core 2; AMD; Dual; NVIDIA GPU

Shareware
Price: $49.00

Description: A GUI utility to remove restrictions from PDF documents, such as printing, editing etc. Acrobat 3.x-9.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 2.71

(18076 downloads)

by ElcomSoft Co.Ltd.

	: not tested
	: not tested
	: not tested
	: N/A
	: Pentium II/III; Pentium 4; AMD; NVIDIA GPU

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.