Well, some users have reported facing a problem that, whenever they try to download and open a PDF file, Internet Explorer will not open PDF files. Sometimes IE just hangs while downloading PDF files.

Fix Adobe Acrobat Reader could not open PDF because it is either not a supported file type or because the file has been damaged error on PC.

If you keep Chrome up-to-date without changing any settings, any PDF you download may open within the web browser by default.

This is especially true of PDF files since Chrome can't open them natively and thus hands them over to other applications, the default being Google Drive's PDF viewer.

These files would not open properly, even after removing the unwanted extension. For example, I deleted the .html extension from a downloaded PDF file, leaving .pdf as the active extension.