An employer can demand the submission of original certificates of educational qualification of a newly appointed person for the purpose of verification, give official acknowledgement for their receipt, keep them for some reasonable time for verification and should return them as soon as the verification process is over. No employer can hold them indefinitely and use them as a hold for any issues pertaining to employment.
Non payment of wages/salary amounting to delay or denial is an offence under the Payment of Wages Act,1936 as well as breach of the contract of employment. Any employer who fails or refuses to pay the incidental expenses related to the discharge of duties of his employees cannot pull up the employee for non performance or under performance.
Politely request the Company to return your original certificates and clear all your dues. If they fail or show no response, make a complaint to the Labor Officer for the area of your work place and file a claim u/s 15 of the Payment of Wages Act,1936 before the Dy. Labor Commissioner who is the Authority under the Act for recovery of the dues if you are a workmen u/s 2(s) of the ID Act,1947 and your monthly gross salary/wages is Rs.24000/- or less respectively.
If you are not a workmen and be firmly prepared for a show down, you may send a legal notice through a Lawyer so as to file a Civil Suit later against the Company for breach of the contract of employment.
Keeping original documents as security to prevent people from absconding or leaving is not as per laid down laws.If employee breaches job contract, the company has legal remedies of damages and specific performance etc.
Send the company a legally drafted letter, but signed by you asking for documents back or file a civil suit.It is time consuming but otherwise there is no way to obtain your documents .