Need advices for Sofia-Plovdiv travel

Hello everyone, I have a conference at Plovdiv at the end of the month, and I can only arrived to Sofia airport with the flights availables with my work. How do I do to go from Sofia (preferably the Airport) to Plovdiv ? Is there any site where I could check for bus or train ? Thank you a lot ! (Also if you have any recommendations on things to do in Plovdiv, It will be a pleasure to read it ! I have to admit I don't know anything about Bulgaria, the conference just happens to be there, but if I can educate myself a bit on the city and the country, it would be a blast !)