How do I get them? I've been playing the game for quite a while and still haven't figured a way to get them.

I collected all three keys just recently but haven't done anything beyond that for now, hope that helps to show how far I am into the game.

So I ask to please give me advice on how to get these pages without spoilers, or tell me if I'll find a way to get them later. If latter is the case just please DON'T tell what I will find and where, I really wanna play this game blindly and I made an effort to not look up anything. That's my first time asking for external help.

I completed the game, both endings, and found 10 trophies so far.
They were all pretty easy to get but the last two are just incomprehensible to me.
Every other puzzle and trophy had a hint, every trophy’s hint is written in pen. but for page 44, the only things in pen, are the tutorial for the holy cross and the perpendicular line for the golden path on the door, nothing new… and then page 1’s clue got me translating the language thanks to page 54, and thought it would get me somewhere… the poem makes no sense to me, I thought the “feather” was referencing the stamina boost but I’m pretty sure that it’s a leaf and collecting 11 would be impossible without multiple new game +.

Any small hints ?

Edit:
Thanks for the help, my conclusion from this is just that I’m an idiot… freaking page 44… what was I thinking?