Hi there, I needed to make notes all over a PDF. For that, I’ve got an iPad Pro with the 2nd gen pen, those notes are thus hand-written.
I thought it would create something like a layer above the original file that I would be able to disable/enable when I need/don’t need those annotations.
Is there something that I miss or did I screw up the original file ? 
Welcome @dunnno
The annotations aren’t baked into the PDF. They can be deleted as needed. But they aren’t something you can hide either.
PS: Hiding annotations isn’t a function of other PDF apps I’m aware of, so you seem to be asking for uncommon functionality.
Thanks for the swift reply 
I didn’t mess the original file 
I found out I could delete what I wrote, thankfully.
So that raises a new feature suggestion : being able to write / draw on files, on layers that are hidable/unhidable.
Even more, being able to create as much layers as needed, like in a CAD software
You’re welcome!
Development would have to assess the request but it’s noted.