Email, Messaging, & Video Calls Email How to Read PDF Documents in Mac OS Mail by Heinz Tschabitscher Writer A former freelance contributor who has reviewed hundreds of email programs and services since 1997. our editorial process Heinz Tschabitscher Updated on October 30, 2018 Apple, Inc. Email Yahoo! Mail Gmail Tweet Share Email You've probably noticed that when you receive an email with an attached PDF in the Mac OS X or macOS Mail application, the PDF sometimes appears as a readable document right in the email and sometimes it appears only as a PDF icon that indicates a PDF is attached. You have to click the icon to view the contents of the PDF in your default PDF reader. Although it isn't obvious, there is rule and regularity to how PDF files are treated by the Mail application. How the Mail App Displays an Attached PDF The answer lies in the length of the PDF. PDF files of only one page are displayed inline in the message text.PDF files with two or more pages are shown as icons. Switch Between Inline and PDF Icon Display in Mail For the single-page PDF files, you can switch between inline and icon display by using the context menu. Here's how: Open the email in the Mail application. Click on the PDF shown inline or as an icon with the right mouse button (or click with the left mouse button while holding down Ctrl or tap with two fingers on the trackpad while the mouse cursor is over the full PDF or its icon) to open the context menu.Select View as Icon from the drop-down menu to display the single page PDF as an icon in the email, or select View in Place to change the PDF icon to an inline document in the email. The View options are not available for multiple-page PDFs.