Edge Classic's PDF Viewer was good, but now Edge's PDF Viewer is just Chromium's and it isn't as good, has half the features (especially for the long-form reading comfortability of the old Edge Classic / Reader), and is a higher security risk (Edge Classic / Reader ran in the UWP sandbox, Chromium PDF is a C++ app running native with much less sandboxing out of the box; Firefox uses PDF.js running in the JS VM/sandbox).