As far as I know there is no European country that grants a partner the same rights as a spouse, so wherever you live it is a good idea to get married. In some countries only spouses or blood relations are allowed to make decisions on behalf of a seriously ill or injured person, so even if you are only abroad for a holiday, not being married could have serious consequences.
Here a partner cannot decide whether life-support should be continued or not, make funeral arrangements or inherit the deceased partner's assets or personal belongings - the nearest blood relation has all of these rights, and it is much the same I believe in any country.
Legally if you are not married to the person you are living with you are his mistress and he is your lover, or if you are of the same sex a lesbian or gay lover.
You can get a lawyer to draw up various documents, but they do not cover pensions or life insurance, unless you are named as the beneficiary, and you need a cartload of documents and the lawyer's bill will far exceed the cost of a marriage licence.