This is all I have for now.
I have not note the first 6 pages, so now it's like this. Assuming I did not miss any pages.
Note* the first 6 and 20 credit to @Tootsy /profile/tootsy.
1. Pyramid, chest in large sand room with bridges through a long, hidden passag
2. Hillsdale – Hug the left side of town by the armor shop.
3. Mt. Matoya – in the last area on the South elevated cliff on the approach to the boss. You can’t miss it. By a chest
4. Kohlingen Auction house.
5. Kohlingen Cave - near the end in a room with lots of crates and a chest.
6. Conall Curach – After the first bridges, its down and to the left between some trees.
7. Nightmare cave - Near North Dock (North east edge of Linblum (South east continent))
8. Arcane Library - Top-left of the area before save point. You have to walk the narrow path along the top wall to the left.
9. Crescent Rivulet - 1st floor, lower-left
10. Dragon King Roost
11. Crystalline Weald
12. Leyton (a town in Ivalice) buy it from a man in the top left house for 5,000G
13. Mount Ozma - First mountain of the merged world. Look for side passage along the main road up the mountain.

14. N/A
15. N/A
16. N/A
17. N/A
18. N/A
19. N/A
20. Tower of Babil (Tootsy)
Please feel free to fill in what you know. 
Change the numbering freely. I just what to order it along with the story line.

For the complete list!

1. Pyramid: Chest located in a large sand room with bridges through a long, hidden passage.
2. Hillsdale: Hug the left side of town by the armor shop.
3. Mt. Matoya: In the last area on the south elevated cliff on the approach to the boss. You can’t miss it; look for a chest.
4. Kohlingen Auction House: you have to bid for it.
5. Kohlingen Cave: Near the end, in a room filled with crates and a chest.
6. Conall Curach: After the first bridges, head down and to the left between some trees.
7. Nightmare Cave: Located near North Dock (northeast edge of Linblum on the southeast continent).
8. Magic Library: Top-left of the area before the save point. Walk the narrow path along the top wall to the left.
9. Crescent Rivulet: 1st floor, lower-left area.
10. Dragon King Roost: Located on the map right before the entrance to the room with the saving point. Before entering the door, go all the way west; there is a narrow path that takes you there
11. Crystalline Weald:
12. Leyton (a town in Ivalice): Purchase it from a man in the top left house for 5,000G.
13. Mount Ozma: First mountain of the merged world. Look for a side passage along the main road up the mountain.
14. Auslen Cave: Entering from the north, in the screen after the one with the levers, just before the stairs going down, there's a secret passage going right. after finding it there is another secret passage south that gives you an excellent weapon for Vahn too.
15. Douzmir Lake: Inside the woodman's hut.
16. Garamonde: A house with no sign. There’s a secret passage on the right side.
17. Cleft of Wind: Go left immediately after entering the green area.
18. Mount Houzell: Go left after entering the cave.
19. The Citadel: In the king's chamber behind the throne. There is no visible paper page; it is hidden inside the far-right dresser.
20. Tower of Babil (Tootsy): last one

Special Shoutouts:

A big thank you to danny89p for finding the page on Auslen Cave; that was a tough one to spot! Also, a shoutout to cpeeta for discovering the last one in the king's room and for locating most of the relics for Bosch! Thank you to everyone else who helped find all these items!

does anyone know what happens when u have all 20? Theres no way i found them all or have the patience to go get them

I had 19 pages after tower of babil and could not find the last one, i had already started the tour of all places to find the last one, then found this topic and sometimes checked some places again to be sure. Nothing, so i started again the tour of the places i had not checked yet. 

In the end i found the last one in Auslen Cave, entering from the north, in the screen after the one with the levers, just before the stairs going down there's a secret passage going right. It seems i missed it the first time i passed through.

Can anyone confirm if this particular hidden or secret passage midway through the left side of the Trabia Base main path has one memoir page? There’s an NPC near the path who says something like, “There’s no treasure left here anymore; we used it for our own survival.” This is a picture of the area in question.

Please let me know to update the main list.

Regards,

So I finally got them all. The Librarian gives you a tome to bring to Kokkul. Was wondering what activated his quest.... VERY nice accessory.

1. Pyramid, chest in large sand room with bridges through a long, hidden passage
2. Hillsdale – Hug the left side of town by the armor shop.
3. Mt. Matoya – in the last area on the South elevated cliff on the approach to the boss. You can’t miss it. By a chest
4. Kohlingen Auction house.
5. Kohlingen Cave - near the end in a room with lots of crates and a chest.
6. Conall Curach – After the first bridges, its down and to the left between some trees.
7. Cave of Nightmares – South passage from the room with the soul mask.
8. Arcane Laboratory - 2nd floor  in room below the stairs.
9. Crescent Rivulet - 1st floor, lower-left
10. Dragon King Roost – To the left of the door in the first big room you come to on a narrow ledge
11. Crystalline Weald
12. Leyton (a town in Ivalice) buy it from a man in the top left house for 5,000G
13. Ivalance Citadel  in the King's room on a bookshelf.
    
14. Mount Ozma - First mountain of the merged world. Look for a passage with a bridge south before going into the first cave.
15. Auslen Cave – From the N entrance, go past the room with the switches, there is a secret passage before the stairs going down.
16. Cleft of Wind – Left side of the stairs in be beginning of outdoor area
17. Douzmi Lake – Inside the woodsman’s hut by the collapsed mine.
18. Mount Houzell – Left after entering the cave on a ledge
19. Garamonde – Secret passage in the house of the guy who sells you the Kasion Key.
20. Tower of Babil – One of the last rooms.

Finally, the last one!!

Citadel (Ivalice capital city) 

King's bedroom - The rightmost bookshelf.

Now, I can go to the moon in peace. lol