Is it possible to get bullet train tickets from shanghai HQ to Hangzhou on the day?

I'm arriving in Pudong airport on afternoon of 26th October and need to go to Hangzhou to meet my friends who are travelling with AirAsia and will land at Hangzhou airport. I'm thinking of taking the metro from pudong airport to Shanghai HQ station, and then taking a bullet train from there to Hangzhou. Do you think it will be possible to buy a bullet train ticket there on the day? I've heard that the bullet train tickets are in high demand, and are often sold out in advance, so its almost impossible to buy a ticket for a train on the same day. Is this true?