Adobe Creative Cloud Design Tools All-in-One For Dummies (2013)
Chapter 6: Securing Your PDF Files
In This Chapter
Finding out about security in Acrobat
Setting limits for editing and printing
Removing sensitive data from PDF files
You may think that because you’ve converted your documents to PDF (Portable Document Format) that they’re secure. This isn’t quite true because Adobe Acrobat includes tools for changing text and images, as well as extracting them for use in other files. For example, you can use several tools to modify text and graphics (see Chapter 4 of this minibook) or copy a passage of text.
Applying security provides you with control over who can view, edit, or print the PDF documents you create and distribute. You can restrict access to files so that users need a password to view them, or you can restrict certain features of Acrobat, which stops most users from manipulating your files. All Adobe applications recognize and honor security settings applied in Acrobat, but some software ignores Adobe’s security settings or can bypass them altogether. For this reason, you should be careful with whom you share your most sensitive PDF documents because even secure PDF files can be accessed by skilled or determined hackers.
In this chapter, we discuss using security protection to limit access to PDF files and show you how to limit what users can do to the contents of your PDF documents.
Understanding Password Security
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. Adobe calls this type of security password security because it requires a password to either open the document or to change the security that’s been applied to the document.
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. You do this by clicking the Tools button on the toolbar and then choosing Protection⇒Encrypt⇒Encrypt with Password to access 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, but the more limited the compatibility.
Remember, not everyone has Acrobat XI. If you intend to share your file with a broad group or if you’re uncertain which versions of Acrobat or Adobe Reader your audience is using, you should allow everyone with Acrobat 7 and later to access your file. 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 because they support much older versions of the free Adobe Reader. In the following list, we explain the compatibility choices before showing you how to enable security in later sections:
Acrobat 6 and Later or Acrobat 7 and Later: If the users who receive your PDF files have older versions of the software, you can select Acrobat 6 and Later or Acrobat 7 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, and secure the file with 128-bit encryption. These security options will keep the average user from gaining access to your files. However, they won’t deter a determined hacker from accessing them and a sophisticated user can circumvent them.
Acrobat X and Later: When sharing files with users who have access to Adobe Reader or Adobe Acrobat Version X or XI, this option provides expanded security, increasing the security level to 256-bit, which makes the resulting PDF files more difficult for unauthorized users to access.
Applying Password Security to Your PDF Documents
Selecting the Encrypt with Password option from the Encrypt button in the Protection section of the Tools panel limits access to the PDF file. Only those who know the password can open the file. However, documents are only as secure as the passwords that protect them. To guard against discovery of a password, use passwords that are eight or more characters in length and include at least one number or symbol and vary the case of the characters. Avoid using words in the dictionary and short passwords. For example, the password Minneapolis is less secure thanM1nneap0lis, which mixes numbers and letters, and includes an uppercase character along with lowercase characters.
To apply password security to a file, follow these steps:
1. With a PDF file open, choose Tools⇒Protection⇒Encrypt⇒Encrypt with Password.
2. Click Yes when the Applying New Security Settings dialog box appears, verifying that you want to apply security to this PDF.
The Password Security – Settings dialog box appears, as shown in Figure 6-1. You can select the Do Not Show This Message Again check box if you do not want this message to appear every time you are securing a PDF file using Acrobat.
3. Select Acrobat 7 and Later from the Compatibility drop-down list.
Although Acrobat XI provides more robust security, few people are using version XI of Acrobat, making it difficult to distribute the file with this high level of security.
4. Select the Require a Password to Open the Document check box.
5. Enter a password in the Document Open Password text box.
Acrobat provides you with guidance about the strength of the password you select, letting you know whether the password can easily be bypassed. You can also add more security settings, which we outline in the next section. Or you can use this setting as the only security to be applied to the document.
If password protection is the only security measure you apply to the document, authorized users can access the document by entering a password. Users with the password may also be able to edit or print the document unless you apply additional security measures. We discuss ways to limit the editing and printing of PDF files in the next section.
6. Click OK.
7. Confirm the password and click OK again. Acrobat warns you that Adobe software honors the security settings, but other tools may allow you to bypass the security. Click OK again and the dialog box closes.
8. Save, close, and then reopen the PDF file.
A password dialog box appears, asking for the password to access the secured file. Every time a user accesses the file, he or she will be required to enter a password.
Limiting Editing and Printing
In addition to restricting viewing of a PDF file, you can also limit editing and printing, restricting users from making changes to your document. This allows users to view a file but not change it.
To limit editing and printing of your PDF document, follow these steps:
1. With a PDF file open, click Tools⇒Protection⇒Encrypt⇒Encrypt with Password.
The Password Security – Settings dialog box opens.
2. In the Permissions area, select the check box labeled Restrict Editing and Printing of the document.
You can now specify a password that will be required for readers to edit the file or change the security settings. (See the preceding section.)
With this option selected, you can apply a password for access to features, such as printing or editing. This password can be different than the password used to open the document — in fact, you don’t even need to use a document open password if you don’t want to, but it’s a good idea to use both of these passwords for sensitive data. If you apply a document open password without a permissions password, it’s easy for an experienced user to bypass the security in the PDF file.
3. In the Change Permissions Password text box, enter a password.
Users who enter this permissions password when opening the document can change the file or the security settings. The permissions password can also be used to open the file, and it provides more privileges than the open password.
4. Choose whether users can print the document by selecting an option from the Printing Allowed drop-down list.
The choices include Low Resolution or High Resolution, or you can prohibit printing by choosing None. The settings you choose here apply to anyone who accesses the document and doesn’t know the permissions password.
5. Select an option from the Changes Allowed drop-down list (see Figure 6-1) to restrict editing.
For the most security, choose None.
6. Select the last two check boxes, if desired:
• Enable Copying of Text, Images, and Other Content: When deselected, this option restricts copying and pasting of text and graphics from a PDF file into other documents. Selecting this option lets users extract text and images from a file by using the simple Copy and Paste commands.
• Enable Text Access for Screen Reader Devices for the Visually Impaired: When you choose Acrobat 6 or Later from the Compatibility drop-down list at the top of the dialog box, you can also select this check box to allow visually impaired users to have the PDF file read aloud to them.
7. When you’re satisfied with the settings, click OK.
Figure 6-1: Restrict what users can edit.
Choosing more advanced security settings, and choosing the latest version of compatibility, runs the risk of your file not being visible to many users who may not have upgraded to the most recent version of the Adobe Reader or Acrobat. Always understand your audience members and the software versions they’re using before distributing files.
Removing Sensitive Data
Sometimes you may want to make a PDF file accessible, but you may want to remove certain sets of information. For example, you may want to remove a person’s name or personal information from a PDF document. You can do this through the process known as redaction.
To redact information in your PDF document, follow these steps:
1. With a PDF file open, choose Tools⇒Protection ⇒Encrypt⇒Black Out & Remove Content⇒Mark for Redaction. Click OK.
2. Use the Mark for Redaction tool to highlight all text to be removed from the document.
3. After marking all text to be removed from the file, choose Tools⇒Protection⇒Encrypt⇒Black Out & Remove Content⇒Apply Redactions. Click OK.
The redacted text is removed from the document.
Note that this permanently removes all content marked for redaction. This cannot be undone. If you are testing this capability, you should first perform a Save As to create a copy of the document so that you do not permanently remove content from a document unintentionally.
4. Click Yes to then remove any hidden information in the file, such as the name of the author or the original document name.
You can also remove this later by clicking the Remove Hidden Information option under the Protection section of the Tools panel.
You can remove specific phrases or words by using the Search & Remove text option found in the Black Out & Remove Content section of the Tools panel.