I don't think you will do this very easily. Google "convert pdf sheet music to audio" and you do get a few results, particularly Myriad's PDF to music, but they say "Because it only processes PDF files that have been exported from a score editor software, PDFtoMusic offers a unique reliability and outstanding results. Therefore, scanned sheet music cannot be managed by PDFtoMusic." You are adding further complexity by the fact that your notation is in devnagri script.
You'd need to do reliable devnagri OCR (Optical Character Recognition) and go from there. Google "devanagari OCR" to get an idea of what is available there, but I have no idea if ony of the available software would do what you need - most seem oriented towards text.Once you can extract music information from your score, generating audio shouldn't be too hard.
