First of, please fill in your device info which you can add it in User Control Panel. That way, you'll get faster replies pertaining to problems with your device.
As for your question, it's just a matter of dragging your PDF e-book file to any e-books folder you assign in your device for your most convenient finding. In my SGS, I created a folder "E-Books" in the external_sd directory. Everytime I want to add books there, I copy paste the files using KIES while doing the routine synchronizing. Once it's put there, I open it using either PDF To Go or ThinkFree Office. You can use other PDF Reader if you like. Some of them have been posted here.
Hope that helps,
