Here is the full list of all 42 Knights of Pen and Paper +1 achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Reach Level 15 in any character.
Unlock the Bard class.
Unlock the Game Developers that made the game.
Continue the game after a game over.
Use a potion while full health.
Make the blacksmith dance.
Win a battle with 7 monsters.
Choose a weird combination of character and class.
Roll 1 in any random roll.
Kill an elite minion.
Reach Level 5 in any character.
Roll 20 in any random roll.
Unlock the Knight class.
Unlock the Necromancer class.
Unlock the Barbarian class.
Unlock the Hunter class.
Unlock the Shaman class.
Kill a dragon.
We know it may be frustrating to die so we've just rewarded you with this achievement. Do not give up, the game is about to begin!
Complete a campaign using all 5 Game Developers as characters.
Play with all classes in game.
Play with all characters in game.
Visit your Kitchen inside the game.
Spend 9.001 golds.
Earn 9.001 golds.
Buy the highest weapon upgrade available.
Buy the highest armor upgrade available.
Reach Level 30 in any character.
Reach Level 30 in a trio.
Reach Level 30 in every character of your group.
Finished the campaign.
Reach Level 15 in a specific Spell.
Unlock a new master.
Unlock all masters.
Gather a grindstone by mining veins.
Gather 10 grindstones from veins.
Finish the storyline as fast as you can (less than 365 days but you may extend that to 465).
Visit every single place in game.
Buy all goodies in game.
Clear a dungeon.
Clear 10 dungeons.
Clear 50 dungeons.