1. Open the PDF file in Adobe Reader.
2. Click File-->Properties menu. A dialog will open up.
3. In this dialog there will be a 'Fonts' tab. Click the 'Fonts' tab. All the fonts used in the PDF file will be listed. If it is a 'Tamil' language pdf file there will also be tamil font listed (bamini, tsc, latha etc). Note down this 'tamil' font used in the PDF.
4. Go to internet download the same font from internet and install the font on your pc.
5. Now open a new word document as well as the tamil pdf file to convert.
6. On the pdf document select all text and do a 'copy' (ctrl + c).
7. Switch to word document and do 'paste' ( ctrl + v).