Cannot scroll pdf files in trackpad after upgrading to Mavericks?

After I upgraded my Macbook pro OS to Mavericks, i can no longer scroll up/down any of my pdf files using the trackpad. I need to use the arrows to scroll the files.

Please help me what to do so that I can use again my trackpad in scrolling the pdf files.

I think there's nothing wrong with my trackpad since i can use it to scroll up/down any other files except pdf.

Thanks