I've been using the Mac Preview app for many years. However, recently, it doesn't appear to have a sidebar anymore. The only way it appears to have sidebar is when opening a document which has more than one page. After some googling, I found a solution. It's a little complicated, but I've made it work :) Open Preview, double-click on the desired PDF, Select Menu > Preferences > Sidebar Scroll down to View > Show Sidebar That's it.