Copy and paste the following in to a new file and save as
IfWinActive ahk_class AcrobatSDIWindow
Sleep is in milliseconds, so
60000 is one minute. You can change this to whatever you want.
Simply run this file, and it should automatically press Page Down automatically. To exit, right click on the icon in the taskbar and choose exit.
You will have to set the zoom level correctly in your reader application to make sure that page down will go to the next page - If not, this script can be modified to the shortcut that does that.
Replace AcrobatSDIWindow with the ahk_class listed for your PDF reader by running AU3_Spy.exe (included with AHK) and focusing on your target application.