In Visual Studio 2015 (as well as previous versions of VS, but you must install Productivity Power Tools if you’re using VS2013 or below), there are two new commands in Visual Studio:
Window.NextTab and
Window.PreviousTab
Just go remap them from Ctrl+Alt+PageUp/Ctrl+Alt+PageDown to Ctrl+Tab/Ctrl+Shift+Tab in:
Menu Tools -> Options -> Environment -> Keyboard
Note: In earlier versions such as Visual Studio 2010, Window.NextTab and Window.PreviousTab were named Window.NextDocumentWellTab and
Window.PreviousDocumentWellTab.