PDF Documents support security methods:
- Password security. You can add passwords and set security options to restrict opening, editing, and printing PDF documents. More about PDF Password Security.
- Certification security. Encrypt a document so that only a specified set of users have access to it.
- Adobe Policy Server. Apply server-based security policies to PDF documents. Server-based security policies are especially useful if you want others to have access to PDF documents only for a limited time.
- 3rd party tools. Acrobat Reader allows third part tools to manage PDF files rights. Some tools such as: FileOpen, locklizard.
Specify the quality of printing for the PDF document:
- Not Allowed prevents users from printing the document.
- Low Resolution lets users print the document at no higher than 150-dpi resolution. Printing may be slower because each page is printed as a bitmap image. This option is available only if the Compatibility option is set to Acrobat 5.0 And Later or a later Acrobat version.
- High Resolution lets users print at any resolution, directing high-quality vector output to PostScript and other printers that support advanced high-quality printing features.
Define which editing actions are allowed in the PDF document:
- None prevents the user from making any changes to the document that are listed in the Changes Allowed menu, such as filling in form fields and adding comments.
- Inserting, Deleting, And Rotating Pages lets users insert, delete, and rotate pages, as well as create bookmarks and thumbnail pages. This option is available only if a high encryption level is selected.
- Fill-in Form Fields And Signing lets users fill in forms and add digital signatures, as well as allowing the actions in the previous option. This option doesn’t allow users to add comments or create form fields. This option is available only if the Compatibility option is set to Acrobat 5.0 And Later or a later Acrobat version.
- Commenting, Filling In Form Fields, And Signing lets users fill in forms and add digital signatures and comments.
- Any Except Extracting Pages lets users change the document using any method listed in the Changes Allowed menu.
Enable Copying Of Text, Images, And Other Content
Lets users select and copy the contents of the PDF document. It also lets utilities that need access to the contents of a PDF file, such as Acrobat Catalog, get to those contents. This option is available only if the Compatibility option is set to Acrobat 5.0 And Later or a later Acrobat version.
Enable Copying Of Text, Images, And Other Content And Access For The Visually Impaired
Lets visually impaired users use screen readers to read the document’s contents. Users can also copy and extract information from the document. This option is available only if Compatibility is set to Acrobat 3.0 And Later.
Enable Text Access For Screen Reader Devices For The Visually Impaired
Lets visually impaired users read the document with screen readers. This option doesn’t allow users to copy or extract the document’s contents. This option is available only if the Compatibility option is set to Acrobat 5.0 And Later or a later Acrobat version.
The standard security provided by Arobat® PDF consists of two different methods and two different passwords, “user password” and “owner password”. A PDF document may be protected by password to open (‘user’ password) and the document may also specify operations that should be restricted even when the document is decrypted: printing; copying text and graphics out of the document; modifying the document; and adding or modifying text notes and AcroForm fields (using ‘owner’ password). More about permission setting.
If user password (also known as password to open) is either not set or known, it is possible to remove permission password instantly. Unfortunately, if a user password is unknown, there is no easy way to recover the password to a PDF document. Universal recovery methods, such as Brute Force Attack and Dictionary Attack, must be used. Unfortunately, due to a nature of an encryption method used in PDF files, the password search is very slow. The brute force speed is usually under one thousand passwords per second even on a top-speed modern PC. It means that long password recovery takes too long time.