The preview program in Mac OS X is actually very easy to use. In addition to looking at pictures or making some simple picture editing and frame modification, it is also considerable for processing PDF files. If you have purchased e-books or magazines, monthly magazines and other contents in PDF format from the Internet and want to transfer them to mobile devices such as iPad, Android tablet or Kindle, if you don't want to be disturbed by the advertisement pages of magazines while reading, or want to minimize the file size, you can try the following methods to delete the specified pages in the PDF file. The following methods are actually completed through the built-in "preview program" of Mac OS X system. Preview program can not only read PDF files, but also delete designated pages in batches, add blank pages, or adjust the order of pages in PDF files. The whole operation is actually quite simple. You don't need to install another program, and you don't need to spend money on software. You can do it with one click. Usage: In step 1, double-click the left mouse button on the icon of the PDF file, and it will be opened by default with the "preview program" built into the Mac system. If other PDF readers or related tools have been installed, you can also right-click the PDF file and click "Application for Opening File → Preview Program" to open the file with the preview tool. Step 2 After opening the PDF document, click "Thumbnail Directory" in the upper right corner, or switch to thumbnail preview mode from "Display Mode → Thumbnail Directory" in the upper left corner of the screen. Step 3 Next, hold down the "Command" key on the keyboard, and then click the page to be deleted with the left mouse button, so that you can select multiple different pages at the same time. Step 4: After selecting the pages to be deleted, click Edit → Delete in the menu in the upper left corner of the desktop, or click Delete on the keyboard directly to delete all these pages. After deletion, close the window and automatically save the current latest status. Step 5 If you want to adjust the order of a page, just click and move it with the mouse.