It's actually not something you would heard spoken vs. in literature. I means "you will (or you have) a lot of problems and sadness". Sometimes people will say "Woe is me" to mean "I have great troubles and sadness" and that is what they mean, but it is usually recognized as a very old literature reference being used to describe their situation. You don't generally hear someone say "woe to you". And if they wanted to align with old literature, they would say "woe is you".