If you are having trouble opening a PDF on Windows 10, it may be because Microsoft Edge (the new web browser for Windows 10) is set to the default PDF viewer.
You will need to change this default from MS Edge to a Adobe Reader.
If Adobe isn't currently installed, click this link to install it: https://get.adobe.com/uk/reader/
Once installed, follow these steps:
Find a PDF on your computer and right click it.
Hover over "Open With" and then click "Choose another app"
Select Adobe Reader and tick the "Always use this App to open PDF files" and click OK.
You should now be able to open PDF's fine.