Ability to go back to earlier pages.
Need to be able to go back in document. Currently can only go forward. What if the reader wants to review something that was read earlier in the document?
the back button should become visible on the left side of the document until you flip over to the second page.
If you are using a tablet or a device with touchscreen support you can also swipe back and forward in the document.
Maybe you can send us a link to your publication and information about the device you encounterd the problem so we can check if there is something wrong with it.