I've downloaded the manual for Heroes of Might and Magic 2, but I can only open it in Microsoft Edge. Does anyone know a workaround for this? I'd really like to be able to have it open on my phone while I learn to play.

Thanks!

After you extract zip archive - you get pdf file. Open if with your prefered app for it (Foxit Reader for example). Or in normal browser (like Edge).

On phone there is more free apps to open it than on PC. Open with any of them. Dedicated to open pdf or apps for pocjet-books that also can open pdf (not all of them able do that).