Aryabhatiya, a manual of astronomy, is the classic text composed by Aryabhata. The text is Sanskrit with the commentary Bhatadipika of Paramadievara. Aryabhatiya in Sanskrit is provided by Sri Sathya Sai Veda Pratishtan. There is an option to download too but the text is not in pdf format. You must also not confuse the text to in Hindi pdf.