However, PDF files that you encounter with your browser will still open in the browser. The following section covers how to make Adobe Acrobat Reader the default PDF viewer for your Edge or Chrome ...

Learn how to always open PDF files in Protected View in Word. Stop Word from opening PDF files in Protected View using GPEDIT or REGEDIT.

As such, it could open a PDF file as long as the %PDF-header started within the first 1024 bytes of the file. There’s, however, a change in the scheme of things now.

The pdf in this thread, for example, will not open. <BR><BR>But this one will. <BR><BR>Can someone with more skill than I examine these links to determine whether there is something about the file ...