couldn't load plugin pdf on Microsoft edge

Recently, Microsoft edge got a problem: when you want to load a pdf file, it can't and shows a message "couldn't load plugin pdf"

To solve the problem: 

upper right corner 

click "...",

click "Settings" 

click "Site permissions"

click "PDF documents"

Enable by clicking to see blue color and the small white ball on the right side

Done

Now, you open pdf file button, you will see a white page, on the lower left corner, you will see "xxx....pdf (file name)" on the first line and "Open file" on the 2nd line, just click "Open file", now you will see the pdf file opened on your Adobe Acrobat reader. 

That's all. Good luck.