Manufacturers usually keep all the old versions of their tablet drivers on their website. If you can't find the driver you need you can always contact customer support and they should be able to help you find it for you.
You may run into problems using an older version of a tablet driver.
A common issue is that the operating system has changed since the driver was first created and applications have also changed in that time. So if you have an older driver you may have difficulty using some features. For example a very new version of Photoshop combined with an older version of the Wacom driver can create a situation where buttons on the pen do not work. The issues you will run into are highly dependent on the specific version of the operating system and the specific version of the application.
Consider OpenTabletDriver