What paperwork do I need to drive from Greece to Bulgaria?

If you are travelling to another EU country as a tourist, you don't need any documentation. However if you are planning to stay long-term in Bulgaria you need to register the car in Bulgaria.

Even though it is not necessary, it is still advisable to have printed form of your car insurance and to check what your insurance covers in Bulgaria. This site has some guidance on how to find what your insurance covers.

Here is an excellent guide: https://www.gov.uk/foreign-travel-advice/bulgaria/safety-and-security#road-travel

The above is guidance by the UK government, particular points are very signifficant:

• there is a small sticker for your car's windshield known as a vignette, it verifies that you have paid road tax ( I think the weekly one is 8 euros). You can purchase one at the border.

• you need to carry evidence for your car's ownership and insurance

• as you might know, your headlights must be on at all times, day and night

As stated by the European Commission here http://ec.europa.eu/transport/road_safety/going_abroad/bulgaria/other_en.htm

You must also have a warning triangle, first-aid kit and a fire extinguisher (small is fine) in the car, also just in case - a hi-viz vest.

And also there is the following legislation:

"Snow chains must be carried from 1 November until 1 March and used when the relevant sign is displayed"(first url).

Considering the weather there now, I would wear chains even on my shoes.