In case you thought you'd heard of every dire threat to your computer, here's one more to add to your list of things to worry about - ransomeware.
This recent Computer World article describes malware that can get into your Windows PC through Adobe PDF files. It will search your computer for various files - Word, Excel, etc. and then makes them unreadable. A message will be displayed demanding $120 to restore the files. This trick has been around for several years but two new recent versions may indicate the threat is coming back.
As with many other computer "dangers", this reinforces the need to keep software up to date and to perform regular backups.