September 2005 Vol. 10 Issue 3
Advanced PDF features can keep documents and users more secure

Editor's note: This is the second of two articles on PDF files. Click this link to read the first article: "Four tips for creating user-friendly PDF files."

You can find documents in Portable Document Format (PDF) everywhere because they're so versatile and easy to create.

Last time, we looked at basic PDF guidelines. This article looks at more advanced PDF features that can make your document stand out and be secure.

PDF password security

The ability to protect information from being copied, manipulated, or pirated is a feature that sets the PDF apart from other easily transferable file formats. You can require people reading PDF files to enter specific passwords to open the files. Also, you can require additional passwords to allow users to copy or print PDF documents.

Password protection is one way to protect information from getting into the wrong hands because the PDF can be encrypted. This will also prevent search engines from seeing the PDF file's metadata (where personal information can be stored). Password protection settings are located under "Document Properties." Click the "Security" tab, then adjust the "Security Method" to "Password Security" (see the image below).

You also can use password protection on a PDF if you intend to sell the material. If you create a unique password for each PDF created and distributed, it is more difficult for others to download and use the files without permission. Adding a unique password to each PDF file would not be effective if large numbers of files are being distributed. If this is the case, you can "Batch Process" a group of files at the same time. Adobe Acrobat ® will apply the same security settings to each file that you specify. You may also use batch processing to perform a number of other repetitive tasks while working in Acrobat ® .

Although no document protection method is 100 percent secure, password protecting your PDF documents makes unauthorized access much more difficult.

Adding JavaScript to a PDF

JavaScript is a "language" that was developed by Netscape Communications to help create interactive Web pages. PDF files can understand an enhanced version of this language, allowing for more control of certain PDF features. Some common uses for JavaScript in PDF files include calculating, formatting, and validating form data, and assigning actions to buttons you create.

If you have a form you want people to fill out and submit back to you, you can add a number of features and enhancements to make sure you capture all the information you intend. You can have form calculations, formatting, and validation. Your PDF also can generate form fields based on what users enter in previous form fields.

Adding menu items, toolbars, and dialog boxes can help end users or PDF creators perform certain tasks. For example, you can add the ability to access database information (not in Acrobat Reader ® ), search features, and additional multimedia controls.

For example, if you have already created a button, right click on it and select "Properties." Then select the "Actions" tab and change the "Select Action" field to say, "Run a JavaScript."

While there are many features you can add or modify with JavaScript, there are many functions you are prohibited from adding or modifying. For example, you cannot add a script to delete the user's hard drive. This is considered a "privileged command." Privileged commands could compromise the security of the PDF file or the user's information.

There are several reference books available that discuss JavaScript for PDF files. Type in "Acrobat JavaScript books" into an online bookstore search and review the results. You also can visit the user forums on Adobe's Web site for additional information about JavaScript.

Digital signatures

A digital signature is a legally binding method to sign a PDF file. In June 2000, President Clinton signed the Electronic Signatures in Global and National Commerce Act (or, ESIGN). Under the act, online/electronic contracts signed in the private sector with an electronic/digital signature, have the same legal force as paper contracts. The only documents excluded from the act are wills and trusts.

Digital signatures are unique to the individuals using them . A person can create a signature or have one assigned. The signature is capable of being verified and it is under the sole control of the person using it.

The digital signature is linked to the PDF so that if the PDF file has been altered, the digital signature becomes invalid. This is a good security tool and protects the end user from using or viewing modified PDF files without them knowing it.

These PDF tools will help you create and provide secure PDF files for you users. If you have other questions regarding PDF security, visit Adobe's Web site where you can find almost any of your questions answered.

Chip Morrison, chip@purdue.edu

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