PDF password protection
Adobe Systems added the ability to protect PDF files with a password.
PDF documents were first developed during the early 1990s as a means of sharing documents among users who had heterogeneous platforms and did not necessarily have the accessibility to mutually consistent application software amongst themselves.
The first edition of the PDF format, 1.0, was released in 1993 by Adobe without any protection or document security features. Since then Adobe have added additional PDF security features such as encryption and digital signatures to the PDF format so that users can password protect PDF files against unauthorized use and add restrictions to prevent editing and printing of content.
The use of passwords for PDF protection is at best, questionable. If you password protect a PDF with an owner password (required to open the document) then you need to give this to those you wish to share the document with. This therefore requires both password management and separate distribution (since sending a password with the password protected PDF is clearly not secure). And if you have applied any restrictions to the PDF then these can be easily removed with free PDF Password Recovery programs.
Adobe Systems added the ability to protect PDF files with a password.
Adobe Systems introduced digital signatures and 40-bit RC4 encryption. From this point on, PDF files began to get encrypted for security purposes and digitally signed for authentication by business users and those who needed an added level of protection when distributing PDF documents. During this stage, there was no other means of access control mechanism for PDF documents and hence passwords became extremely common across the world and were used by a majority of users, simply because there was nothing else available at the time.
Adobe adds 128‑bit RC4 encryption for PDF Password protection.
Adobe added the ability for sections of content to be hidden in a PDF document and usage right signatures to validate that permissions had been granted by a bona fide authority. Adobe Reader verifies that the signature uses a certificate from an Adobe-authorized certificate authority.
Adobe adds 128‑bit AES encryption in Adobe Acrobat 7.0 & Adobe Reader 7.0.
Adobe changes password checking method in Acrobat 8 to speed up password authentication. This introduced a serious security weakness that PDF Password removal software took advantage of to remove PDF owner passwords 100 times faster than before.
Adobe handed over the PDF standard to the ISO organization which meant they could no longer release new versions of the file format. Instead they added custom features to PDF that only their own software supports. In 2008 they added AES 256 bit encryption. Other PDF creation companies followed suit.
Version 2.0 defines 256-bit AES encryption as standard.
![]() |
Types of PDF Password |
The basic level of security provided by Acrobat PDF consists of two differing measures and two password controls – one being the use of a password which enciphers the file and forbids the opening of the document (owner password), and another password (permissions password) which determines operations that should be restricted even when the document is decrypted. This could include various processes such as printing the document, copying the text or the content from the document, duplicating graphics from the document, modifying the content of the document or adding or deleting notes and text within the AcroForm fields.
![]() |
Is PDF password protection secure? |
Most people are of the opinion that PDF password protection helps to keep their PDF data secure and safe. However, this is not entirely true. Although passwords have been the most common form of security by which users prove their identity to a PDF file, it has also been the most vulnerable. Experts recommend that PDF password protection should not be widely used, especially to safeguard confidential information.
Since protecting PDF files with passwords is not much better than not doing so, why is PDF password protection so widely used? One of the main reasons why password-based authentication of PDF files has become so common is not because of the security that it offers but because of the ease of use, low cost, simplicity and practicality. Almost every PDF creation application has PDF password protection functionality built-in, and that provides a quick and easy security option for users.
There are a number of aspects that determine how safe such “PDF password protected” files really are.
PDF password protection is therefore not a secure form of protection for sensitive information that must be tightly controlled.
![]() |
Is PDF Password Protection right for my business? |
When deciding whether PDF Password Protection is right for your business, consider the following points:
You may find that PDF password protection is probably only right for your business if the information inside your PDF files is not of any specific value. This is because:
![]() |
What are the alternatives to PDF password protection? |
If you want actual security for your PDF documents then choose a system that does not rely on passwords for its security.
Locklizard provides PDF security software that protects PDF documents without passwords (we use transparent public key technology so that keys are never exposed to users), and enforces their use wherever they reside.
We automatically lock PDF files to authorized devices so they cannot be shared (and locations too if you want stronger security), and prevent printing, stop screen grabbing, watermark content with dynamic watermarks (user details, date/time stamp, etc), and enable the document owner to expire and revoke content at any time.
We use our own PDF Viewer software rather than plugins to native appliations so that your PDF files cannot be compromised by known (and unknown) security weaknesses. Read our DRM technology to see why Locklizard is superior to PDF password protection and how we protect your PDF files not matter where they reside.