Start by opening the folder that has your PDF file in Finder. RELATED: Use Your Mac’s Preview App to Crop, Resize, Rotate, and Edit Images To convert a single select page from your PDF to JPG, use Mac’s built-in Preview app. We’ll show you how to perform this conversion using the built-in Preview and Automator apps on the Mac. On a Mac, you can use just the built-in tools to convert specific or all pages of a PDF file to JPG.