Here is my issue: I am writing a document with a lots of design and art work. Suppose I have filled page “A” with lot of content non sequentially. Now I’ve moved on to next page “B”. Accidentally I draw somethings on page B. Then as per my habit I tap undo couple of times, now if unknowingly do more undos than the changes on page B. It undos changes on page A as well. If I don’t notice it then I’ve lost last content put on page A. If I notice it, then I have to press redo till I make sure nothing has been lost. Which wastes some time, plus induces some paranoia.

Can you restrict undo operations to the current page only? I mean what’s the point in continue doing undo operations on pages which are not visible(or not in front of us) at that moment?
Same case can be said about redo operations.
In other words can you maintain user actions separate for each page? So that undos on current visible page doesn’t affect non visible pages.

I know there is a “clear page” feature. But it can’t be used when I have some content already on page B.

Further discussion with support team:

If we stored undo information for the current page only, it wouldn't be possible to undo something on a previous page even after we scroll to it.
You could maintain an undo queue/stacks for each page that the user has done modifications on, in that edit session. You don't have to maintain undo queues for all the pages in the document. You need to maintain the queues only for the pages that the user has modified so far, from opening of the Goodnotes app and opening the document.
When the user scrolls to the previous page, bring up that page's undo list, which will be separate from the next page.

However, I can imagine how the current behavior can still work in the user's advantage in case they need to be able to undo something on a previous page.
Why would a user want to undo things on the previous page while staying on the current page? Naturally they would navigate to the previous page and then do undo/redo operations that they certainly will prefer to be happening in front of their eyes.
If you are concerned about previous page's undo operations, you can maintain in separate list for that page as explained in previous point.

Same discussion also applies to "redo" operations.