All of a sudden all my saved PDF files in Windows 10 have been change to Avast HTML.Document - As well as when I scan files to .pdf on a usb stick they show up as Avast HTML Documents... very frustrating and haven't found a solution, hopefully until now, on here
You may already have figured this out. But I just got a laptop with Windows 10, and the same thing happened to me. I fixed the problem by doing the following:
1. Right-click on any Avast HTML document
2. Select "Properties" at the bottom of the drop-down menu
3. When the window pops up, it should be on the "General" tab view
4. In this pop-up window, look for "Opens with:", and you'll see the program currently associated with the file (in this case "Avast HTML Document"); next to this will be a "Change" button
5. Click on the "Change" button. When another window pops up asking "How do you want to open [current program] files from now on?", click on "More apps" under OTHER OPTIONS and select Adobe Acrobat.
6. Click OK,
7. Exit.
You should be all set. Note: If the "Change" button is grayed out, then that's another issue, and unfortunately I don't know how to work around that.