Adding write protection to your PDF files prevents edit-happy readers from making changes to your text. Adobe Acrobat has built-in encryption capabilities that enable you to write-protect a PDF. Acrobat also adds this functionality to some Microsoft Office programs when Acrobat and Office are installed on the same computer. Several online alternatives exist for people who don't want to spend a mint for a copy of Acrobat.
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Add Write Protection in Adobe Acrobat
To set permissions to read-only in Adobe Acrobat XI, start by clicking the Tools pane. Open the Protection panel, click "Encrypt," click "Encrypt With Password" and, when prompted, confirm that you want to add write protection to your document. Here you can specify whether you want to restrict both editing and printing. You can also add full-on password protection so that a user must enter a password before opening the file at all. After selecting your permissions settings, you must confirm your chosen password and then save the document with a new name to apply your new write protection.
Add Protection in Microsoft Office
If you have both Acrobat and Microsoft Office on your computer, you can also add write protection to a document when you export it to a PDF from certain Office programs. Compatible programs include Word, Outlook, PowerPoint and Excel. Launch the program from which you want to export the protected PDF, click "Acrobat" at the end of the ribbon and select "Create PDF." The available options are the same as those in Acrobat itself. In addition to restricting editing, you can control printing, the copying of text and images, and dictate whether you want to let visually-impaired users have textual access.
Add Write Protection Online
Several third-party websites enable you to add write protection to PDF files as well (links in Resources). In most cases, you upload your PDF, select which permissions you want to apply to the document, enter a password and then click a button that converts your initial file to a new document with updated permissions. Some of these websites have size limits that restrict you from adding write protection to large PDF files.
Permissions and the Limits of Write Protection
Although adding write protection to a PDF file provides a degree of protection, a number of third-party tools have been developed to easily defeat or crack these passwords. Do not assume that a write-protected PDF document is absolutely safe from prying eyes.
To add another layer of protection to an important file, consider saving it to a password-protected external hard drive or USB key. Pro and Enterprise versions of Windows 8 feature a tool called BitLocker that enables you to encrypt folders. A number of third-party security programs enable you to create password-protected folders into which you can place your write-protected PDF for additional security.