I guess people are down-voting you because it's a simple google search away. However, to answer your question:

On Atom, I've set ctrl + tab to remap to pane:show-next-item, and ctrl + shift + tab to pane:show-previous-item.

(view your keymap, and see what ctrl + page-up/down is bound to, and then bind it to ctrl + tab /+ shift)

Edit: here are my settings:

   'body':
     'ctrl-tab': 'pane:show-next-item'
     'ctrl-tab ^ctrl': 'unset!'
     'ctrl-shift-tab': 'pane:show-previous-item'
     'ctrl-shift-tab ^ctrl': 'unset!'