The encryption they use is unbreakable other than by them. We can remove the virus so that the computer is usable again but you will either have to recreate the documents, recover them from a backup or pay the ransom.
One way to avoid this virus is to NEVER open an email attachment unless you know the sender meant to send it to you.
One way to keep this kind of thing from being much of a problem is to have a good backup system so you have something to recover.
If you do get an infection like this, turn off the computer as soon as you notice. If not it could affect other machines in the same house or office.