I am amazed such a popular extension, pdf, is not a standard part of the file viewing feature. I have yet to find how to install a new plugin into the viewer. I would appreciate help. Thanks in advance
Just install almost any PDF viewer, the same as with File Explorer. Adobe Reader, PDF-XChange, Sumatra (requires ticking an extra option in its installer), among others.
Thanks for the kindness of your reply and instructions. Will try