Usage permissions in PDF files
Everybody knows that most of the documentation distributed over the Internet is published in the PDF format. After publishing a document, authors usually make a few considerations with regards to how the content should be used by those reading the PDF. Should printing be allowed? Should copying of text be allowed? Should extraction of images be allowed? This is most commonly observed when opening a government-issued PDF form; more often than not, one will notice a message in the toolbar of the PDF viewer being used:
Fig.01 – Restriction warning in Nitro PDF Professional
One might question why a PDF form or document would be locked down when it is freely available on the web. Well, in the case of government forms, the government department must guarantee the authenticity of the document as well as safeguard the intellectual property contained within. Most other publishers just wish to restrict the way a document is accessed, for example by disabling content-extraction and printing to prevent unauthorized distribution of the images contained in a PDF file.
The levels of password protection
Essentially, one can assign two basic levels of password-protection to a PDF file:
- Access password: restrict access to the PDF file.
- Usage password: restrict what can be done with the PDF file.
In first option, access passwords prompt the viewer with a password dialog before the PDF file is opened. This is pretty much self-explanatory since the file cannot be viewed unless the correct password is known. When the document’s author configures an access password, the chosen password is encrypted and stored inside the PDF file. All PDF viewing applications are designed to look for this password and enforce it by prompting the user before the document’s content is made available.
With the second option, an author can set a usage-password to restrict the operations a PDF viewing application can perform with the file. The following list details the level of control offered when setting usage-passwords:
- Printing:
- Prevent printing.
- Allow low-resolution printing.
- Allow high-resolution printing.
- Changes:
- Prevent all changes.
- Allow creation, insertion, rotation, and deletion of pages.
- Allow filling-in of form fields and signing.
- Allow commenting, filling-in of form fields, and signing.
- Allow all changes, but prevent page-extraction.
- Content:
- Allow/prevent copying of text, images, and other content.
- Allow/prevent text access for screen reader devices for the visually impaired.
When to secure your PDF files
The most common misinterpretation of the PDF format is that converting a file to PDF will prevent any unauthorized changes from being made to it. You might wonder; if that statement is not correct then what’s the point of converting to PDF? The biggest strength of the PDF format is its ability to reproduce documents consistently across any operating system or computing platform. PDF is not the right choice for word processing or editing documents, however it is easy to edit the text in an unsecured PDF file using products like Nitro PDF Professional, which has a flexible array of text insertion and editing options.
How to secure your PDF files
Existing users of Nitro PDF Professional are most likely to be already familiar with the options offered to configure a document’s properties, where one can also apply PDF protection to partially or completely secure the document. On the other hand, if you’re after a free solution to create and secure PDF files, Nitro PDF Reader does exactly that. Although you cannot change security levels on existing PDF files, you can secure new PDF files you create with Nitro PDF Creator. When securing PDF files using Nitro PDF products, the same security levels will apply regardless of the application used to open the PDF file. So if you secure a PDF using Nitro PDF Professional, the document will be equally protected if it is opened in Adobe Acrobat or Foxit Reader.
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