From Prague Vaclav Havel Airport to the main railway station
The simplest way is to take the direct bus, which leaves 2 – 4 times an hour. The AE bus leaves from the bus stops outside both terminals of the airport (flights from/to Schengen countries use terminal two, other flights use terminal one). The bus departures board shows clearly when the next bus leaves. The service is quite frequent, and you can buy a ticket from the driver for 60 crowns when you get on the bus. For the return journey, you can buy a ticket directly from Pardubice main station to Prague airport, as the AE bus is a service of Czech Railways (not a Prague city transport service). The journey time is 46 minutes.
The 119 bus goes from the airport to Nádraží Veleslavín metro station (green line) and on from there to the main railway station. Buy a 32 crown ticket from the Prague City Transport booth inside the terminal building, or a one-day or three-day ticket, before you get on to the bus – or buy a single ticket from the bus driver (from the airport only) for 40 crowns! This route is good for getting into town, but it is currently inconvenient for getting to the railway station, as the green line metro does not stop at Muzeum in the direction from the airport. You have to continue until the next stop, and then take the train back in the direction to the airport and get out at Muzeum. And then change to the red line and go to Hlavní Nádraží (main station).
The 100 bus goes to Zlicín metro station (green line). Change at Florenc to the red line, and go to Hlávní Nádraží (main station).
From Prague Hlavní Nádraží (main station) to Pardubice Hlavní Nádraží (main station)
At the main railway station, English language can be used. Buy a ticket to Pardubice, or a return ticket. Group tickets and return tickets are a bit cheaper, but all ticket prices are very reasonable, a fraction of what you would pay in western Europe. There are frequent fast trains to Pardubice. Most fast trains are comfortable, and with any luck you will have a very pleasant journey. The 100 km journey to Pardubice takes less than an hour. A second class ticket is fine. First class is a little finer. Note that your Czech Railways (České drahy) ticket is not valid for Regiojet trains (denoted RJ) or for Leo Express trains (denoted LE). Regiojet and Leo are private companies, and their tickets can be bought in their offices at the station, and include a compulsory reserved seat.
Reservations can be made on some Czech Railways (České drahy) trains and are required (sold automatically with the ticket) on Czech Railways Pendelino trains. A reservation or a first-class ticket is recommended on a Friday afternoon out of Prague and on a Sunday evening into Prague, when trains are likely to be crowded.
Taxi are to be avoided by foreigners in the Czech Republic, as we are generally considered ‘fair game’. Uber may be less unreliable, as they try to stop their drivers setting their own prices. If you need to take a taxi to Prague airport to catch a Sunday evening flight, get someone with local knowledge to help you negotiate a price and to locate your driver. A taxi driver can get you from Pardubice racecourse to Prague airport in about two hours. A taxi from Prague airport to Pardubice is not recommended.