Lao Airlines have flights to Pakse from Luang Prabang, Vientiane, and Savannakhet. International routes flying to Pakse are from Siem Reap, Ho Chi Mihn, and Bangkok.
You can hire a car, van, or (better) 4WD vehicle in Pakse. For the more younger and adventurous traveller a 250cc motorbike is also possible for rental.
Several buses depart Vientiane’s Southern Bus Terminal for Pakse and onward travel to Attapeu every day, though schedules (and conditions) may vary. Categories of buses range from less-than-comfortable busses making local stops, to VIP coaches and overnight sleepers with direct routes to Pakse. To make your long journey down south more comfortable, research online or double check with your travel agent which type of bus you booked. A personal preference of falangs is the Kring Kai bus that departs daily at 20:30 (for both Vientiane and Pakse bound buses).
Once in Pakse, travelers can head onward to Attapue via Paksong in the Bolaven Plateau throughout the day. Check again with your travel agent which bus is best for your needs.