PDN stands for Portable Draughts Notation, basically it is a text file suitable to load into different programs.
The programs use their own format to store games but they all can export and import using PDN format.

This is what PDN game looks like:

[Event "Online games"]
[Site "Playdraughts.com"]
[Round "0"]
[Date "2015.03.14"]
[White "Tindo"]
[Black "Tutor"]
[Result "2-0"]
[GameType "23,W,8,8,A1,0"]
1. c3-d4 d6-e5 2. b2-c3 e7-d6 3. e3-f4 b6-a5 4. f2-e3 c7-b6 5. c1-b2 b6-c5 6. d4xb6 a5xc7 7. a3-b4 a7-b6 8. b4-a5 f6-g5 9. c3-d4 e5xc3 10. b2xd4 g5-h4 11. a1-b2 h4xf2 12. e1xg3 f8-e7 13. b2-a3 d6-c5 14. d2-c3 c7-d6 15. a5xc7xe5 e7-f6 16. d4xb6 f6xd4xf2xh4 17. h2-g3 h4xf2 18. g1xe3 g7-f6 19. a3-b4 f6-g5 20. b4-c5 h8-g7 21. c5-d6 g7-f6 22. d6-c7 b8xd6 23. b6-a7 g5-h4 24. a7-b8 d8-c7 25. c3-d4 h6-g5 26. f4xh6 h4-g3 27. h6-g7 f6xh8 28. d4-c5 d6xb4

Notice the Game Type - the first numer denotes the type of game, in this case 23 - Pool Checkers. Russian Checkers games are of type 25.
You can practice downloading PDN from http://poolcheckers.com.
1. Click e-library
2. Click Playdraughts Games
3. Scroll to the bottom of the left column to find "Download these games in PDN"
4. Click PDN, this will open the text file in the right part of the screen.

You can try Copy/Paste the text, but a simpler thing is to come back one step, right-click the word PDN as click Save target as.
Some computers do not recognize PDN extension and might save the file with .TXT, you can later rename it back to PDN.
Generally save your pdn to the Bases directory (see below)