The main difference between a public document and a work in the public domain is that public documents are created for public use, while works in the public domain are not owned by anyone:
These are documents that are created for the public to use, such as police records, land revenue records, and records from regional development authorities.
Works in the public domain are works that are not protected by copyright, trademark, or patent laws, and are owned by the public. Works in the public domain are free to use, copy, and distribute without permission or citation. They can be used as the basis for new creative works. Works enter the public domain when their copyright expires.
No permission is needed to copy or use public domain works. A work is generally considered to be within the public domain if it is ineligible for copyright protection or its copyright has expired. Public domain works can serve as the foundation for new creative works and can be quoted extensively.
Whereas, Public Documents are documents or records that are authenticated by the public officer. Public documents also contain statements made by the public officer in his official capacity that are admissible as evidence of the fact in civil matters . They are made available to the public for reference and use.
For example: Copy of the chargesheet along with the necessary documents cannot be said to be public documents within the definition of Public Documents as per Section 74 of the Evidence Act.
Information obtained under the RTI Act is part of the documents held by Public Authority, who are Gazetted officers. A certified copy of a document received by virtue of the RTI Act is secondary evidence as provided under Section 63 of Evidence Act, 1872.