Viewer Pane problem with pdf files

[Leo]

Your PDF viewer is broken and may need reinstalling.

Presumably PDF viewer in is also not working in Explorer's viewer pane?

Some suggestions are here, but I would first try just reinstalling whichever PDF viewer you use, as that often solves the problem.

PDF-XChange preview handler hangs

You probably need to (re-)install a PDF viewer, one which includes a preview handler. PDF-XChange has a viewer but I don't know if their Editor Pro package includes it, or if it's a separate thing. I would get it working in File Explorer first, th…