Increase paid up capital

Hi,

If a Pvt ltd co. whose paid-up capital is 19900000, and authorised capital is 20000000  wants to increase its paid up capital by issue of debentures what is the documents and formalities required to be followed?

If it opts to issue convertible or non-convertible debentures to whom they should issue ? which type of debentures would be benificial for the company?

Please reply its urgent

Regards

Namrata