Select the open document on your Mac by using ⌘-click ; 2. Then click the lock in the bar at the top. 3. Then click Encrypt ; 4. Click the lock again on the top of the window ; 5. Click Continue. How to Open a PDF on your Mac with Apple Pay: 1. Select the open document in Apple Pay on your Mac (it is probably already open); 2. Click on the lock bar in the top right corner, then click and choose the file to open; 3. Click encrypt ; This tutorial describes how to do this using a version of Apple's Mac OS X called Lion. In Lion Apple does not support encryption for any type of file save as .pdf or .doc, and it is therefore not possible to get a copy of an encrypted PDF as a file of any save as type. For this purpose we will use the file extension Open.doc which is open .pdf but is not actually of file types the operating system supports. We will use an Open.doc from the following file on the disk: Encrypting a PDF in Disk Utility To encrypt a PDF file using Disk Utility click on Disk Utility from the Applications menu > Utilities. Then in Disk Utility click on the disk icon and choose the partition you want to open the file in. In our case it's the partition that contains Preview, the operating system and all the programs that we already have on it. Click on the View button at the top and in the window that appears choose To encrypt File. Click the Encrypt button and your computer will create a disk-encryption partition, which will be called “Untitled” in a future update of this tutorial.