For now I am molding HeFullScreenButton code to become a generic HeOverlayButton (later I will try to make HeFullScreenButton simply inherit from HeOverlayButton with a fixed position and icon).

Once I have them I simply have to show them when a user taps on the Hand icon. They will disappear after a few seconds of inactivity.
They will reappear if you tap on the screen or after panning around.

Once tapped the buttons will do what we just said.

Summarizing we'll have one button on the right of the screen and one on the left of the screen (both vertically centered) that when tapped will change page (when we reach the first or last page they'll show as a cross and will add a page either at beginning or end).

Following De Bernardis suggestion I may put two more overlay buttons on the top of the screen to add a page before or after the current one.

Or, just one icon that always adds AFTER the current page.
So if you want to add a page before the current one, simply move back one page.

We'll see...