Here is the full list of all 21 Lost Words: Beyond the Page achievements.
Thanking You
Start something new
Finish Chapter 8
Find all the Fireflies
Light all the torches
Finish Chapter 7
Unlock your full potential
Finish Chapter 6
Topple all the frozen Seakin
Collect every black asterisk
Finish Chapter 5
Do all the washing up
Finish Chapter 4
Into the pie-byss
Finish Chapter 3
Finish Chapter 2
Help the villager
Finish Chapter 1
Ring the bell in E1
Collect the items in Estoria 1
Loop the page for 5 seconds