Understand Password Security in Acrobat CS5
Adobe Acrobat Creative Suite 5 security features provide you with the ability to restrict who can view, edit, or print the PDF documents you distribute.
By requiring users to enter a password to open and view your PDF files, you limit access to those files so that only certain users can view them. You can also apply security to limit access to certain Acrobat and Adobe Reader features, such as copying text or graphics, editing the file, and printing.
Apply security options to limit the opening or editing of your PDF document, restricting these capabilities to users who have been provided the proper password. This is done by clicking the Secure button on the Tasks toolbar. If the Secure button isn’t visible, choose View→Toolbars→Tasks.
Click and hold down the Secure button in the Tasks toolbar and choose 2 Encrypt with Password to bring up the Password Security - Settings dialog box.
In the Password Security - Settings dialog box, choose an Acrobat version from the Compatibility drop-down list. The higher the version of Acrobat, the greater the level of security.
Your choice here is based on your needs for security and also the version of Acrobat or Adobe Reader that your audience uses. Lower versions of Acrobat provide more compatibility with the widest number of viewers, as they support much older versions of the free Adobe Reader. These are the compatibility choices:
Acrobat 3 and Later: If the users who receive your PDF files may have older versions of the software, you can choose Acrobat 3 and Later from the Compatibility drop-down list to ensure that the recipients can view the PDF file you’re securing.
This option provides compatibility for users who may not have updated their software in many years, but the level of security is limited to 40-bit encryption. Although this amount keeps the average user from gaining access to your files, it won’t deter a determined hacker from accessing them and can be easily circumvented by a sophisticated user.
Acrobat 5 and Later: When sharing files with users who have access to Adobe Reader or Adobe Acrobat Version 5 or 6, this option provides expanded security, increasing the security level to 128-bit, which makes the resulting PDF files more difficult to access.
Along with the enhanced security, you can also secure the files while still allowing access to the file for visually-impaired users. Earlier versions of security don’t provide this option, but it’s included when you choose either Acrobat 5- or 6-compatible security.
Acrobat 6 and Later: Along with the enhanced security offered with Acrobat 5 compatibility, this setting adds the ability to maintain plain text metadata. In short, this option allows for information about the file, such as its author, title, or creation date, to remain visible while the remainder of the file remains secure.
Acrobat 7 and Later: This choice includes all security options of Acrobat 6 compatibility and also allows you to encrypt file attachments that are part of a PDF file. It uses the Advanced Encryption Standard, which is a very high level of encryption, making it unlikely that an unauthorized user can decrypt the file without the password.
Acrobat 9 and Later: Choose this option if your audience is using the latest version of Acrobat and you need more advanced security. The encryption improves to 256-bit AES, making the file much more difficult for even the most determined hacker to access.