What is Public Document and Private Document? Is the certified copy of public document admissible in evidence?

Documents are mainly of two types private and public documents. 

Under Section 74 Public Document is defined - 
The following documents are public documents:-
(1) Documents forming the acts, or records of the acts
(i) Of the sovereign authority,
(ii) Of official bodies and tribunals, and
(iii) Of public officers, legislative, judicial and executive, [of any part of India or of the Commonwealth] or of a foreign country;
(2) Public records kept [in any State ] of private documents. 

Under Section 75 Private Documents are defined 
All other documents are private 

Section 76 Certified copies of public documents - 
Every public officer having the custody of a public document, which any person has a right to inspect, shall give that person on demand a copy of it on payment of the legal fees 
therefore, together with a certificate written at the foot of such copy that it is a true copy of such document of part thereof, 
such certificate shall be dated and subscribed by such document of part thereof, as the case may be, and such certificate shall be dated and subscribed by such officer with his name and his name and his official title, and shall be sealed, whenever such officer is authorized by law to make use of a seal; and such copies so certified shall be called certified copies.

Section 77 Proof of documents by production of certified copies - 
This section states that the certified copies may be produced as proof of the contents of the public document or a part of them of which they purport to be copied. 

Section 78 Proof of other official documents -
The following public documents may be proved as follows-
(1) Acts, orders or notifications of the General Government in any of its departments, or of the Crown Representative or of any State Government or any department of any State Government-
By the records of the departments, certified by the heads of those departments respectively, or
By any document purporting to be printed by order of any such Government or as the case may be, of the Crown Representative.
(2) The proceedings of the Legislatures-
By the journals of those bodies respectively, or by published Acts or abstracts, or by copies purporting The Orient Tavern be printed by order of the Government concerned.
(3) Proclamations, orders or regulations issued by Her Majesty or by the Privy Council, or by any department of Her Majesty’s Government-
By copies or extracts contained in the London Gazette, or purporting to be printed by the Queen’s Printer.
(4) The Acts of the Executive or the proceedings of the Legislature of a foreign country-
By journals published by their authority, or commonly received in that country as such, or by a copy certified under the seal of the country or sovereign, or by a recognition thereof in some Central Act.
(5) The proceedings of a municipal body in a State-
By a copy of such proceedings certified by the legal keeper thereof of by a printed book purporting to be published by the authority of such body.
(6) Public documents of any other class in a foreign country-
By the original, or by a copy certified by the legal keeper thereof with a certificate under the seal of a notary public, or of an Indian consul or diplomatic agent, that the copy is duly certified by the officer having the legal custody of the original and upon proof of the character of the document according to the law of the foreign country.

Section 79 Presumption as to the genuineness of certified copies - 
This section states that the court shall presume a document to be genuine if it is a certificate or a certified copy. Also, any document, which is by law, declared to be admissible as evidence and has been certified by an officer of the central or the state government or of Jammu and Kashmir and is authorized by the center. Provided, that the document is executed in the form as prescribed by the law. 

Section 80 Presumption as to documents produced as records of evidence. - 
This section states that when a person has appeared before a court and has recorded testimony or confession and his statement being relevant in another case, a certified copy is produced; the court shall presume it to be genuine.  

For Better understanding watch this video -