There are specific documents which are required for preliminary stage to final stage of land transaction, Further it can be categorized under three prominent categories;
Details about transfer of ownership details, area and cost of land
Record of rights:
Details about property transactions from time to time, rightful persons and their rights, nature and limits of rightful persons, revenue paid details, any community and government rights, mortgage or loan details. * the rights could be ownership, long-term lease hold, tenancy)
Spatial land records:
Revenue map (land boundaries, plot area, connectivity with roads, presence of water bodies, surrounding area details), Land use (agriculture, residential, commercial, industrial etc.), Land topology/ topography (natural features esp. shape)
The documents can be procured either offline or online mode, your land location sub registrar office will be the ideal place to get all offline records and for online docs there are certain state/central gov websites to help you with. In karnataka it is https://landrecords.karnataka.gov.in/
*presently most of the documents are digitised over gov website, however there could be certain documents not available digitally.