Power Apps Authoring Version 3.24122.12 makes the PDF controls (see image below) of a PDF Viewer control disappear, even when the Show Controls property is set to true. This occurs inside Power Apps Studio and also on all devices using the app published by that authoring version.
When a screen is opened in the app, the controls appear for a split-second and then disappear. Users then cannot interact with any of those controls, e.g. search, page navigation, etc.
The issue was temporarily addressed by rolling back to Authoring Version 3.24121.10