*Update 01/23/2018 - added the four 'The Hidden Ones' DLC Papyrus Puzzles*
There are 25 Papyrus Puzzles in the game (without the DLCs) If you pick up a papyrus it will give you a clue for the location. To solve the Papyrus Puzzle find out where the location is and loot the item. Each Papyrus Puzzle gives you 300 coins, 500 experience and a rare or legendary Item (weapon or armor).
Here is the video solution for the first available papyrus in Siwa called A Long Drink
In the spoiler are all papyrus puzzle as video links but beware this spoiler / content is huge!