PDI
PDI may refer to:

Organisations
Investigations Police of Chile (Spanish: Policia de Investigaciones de Chile), the state police force of Chile
Party for Justice and Integration (Albanian: Partia për Drejtësi dhe Integrim), an Albanian political party
Pacific Data Images, former American computer animation production company
Philippine Daily Inquirer, a broadsheet newspaper in the Philippines and the Philippines' newspaper of record
Plumbing & Drainage Institute, an American plumbing products manufacturers certification organization
Ideal Democratic Party, political party in Rwanda
Partai Demokrasi Indonesia (Indonesian Democratic Party) (1973–2004), a defunct political party
Polo Democrático Independiente (Independent Democratic Pole), a Colombian leftwing social democratic political party

Chemistry and biochemistry
Pyridinediimine, organic compounds used as ligands
Perylenediimide, a member of the rylene dyes
Protein dispersibility index, a means of comparing the solubility of a protein in water
Protein disulfide isomerase, an enzyme which catalyzes the formation and breakage of disulfide bonds in proteins
Polydispersity index, a deprecated term for the molecular weight distribution of polymers

Computing
Pentaho Data Integration, Pentaho Data Integration (PDI, also called Kettle) is the component of Pentaho responsible for the Extract, Transform and Load (ETL) processes.
Personal Data Interchange, an information sharing standard developed by the Versit Consortium
Portable Database Image (.pdi), a file format to store structured databases for reporting and analysis in a highly compressed way
Program and Debug Interface, an Atmel proprietary interface for external programming and on-chip debugging of computing devices.
Projected Digital image, a digital image used for projection, often in the context of a photographic competition

Other
Postal Development Indicator, a ranking developed by the  Universal Postal Union
Peripheral drift illusion, a motion illusion generated by the presentation of a sawtooth luminance grating in the visual periphery
Pilot direction indicator, an aircraft instrument that guides a bomber pilot during a bomb run
Power Distance Index, a statistic in anthropology and social studies that is used to describe the degree of acceptance of unequal power distribution in a society or group
Powered Descent Initiation, the maneuver of the Apollo Lunar Module as it descended from lunar orbit to landing
Pre-delivery inspection, the examination of a car, home, or other traded goods before handover to the new owner.