(polymers) Initialism of polydimethylsiloxane.

Initialism of pre-delivery inspection. / Initialism of polydispersity index. / (automotive) Initialism of petrol direct injection. (fuel injection)

(mathematical analysis) Initialism of partial differential equation. / (software) Initialism of plugin development environment. / Initialism of pulse detonation engine.

(linguistics) Initialism of present-day English.

(electronics) Initialism of personal digital assistant. / (colloquial) Initialism of public display of affection. / (computing theory) Initialism of pushdown automaton.

Initialism of Product Data Management. / (signal processing) Initialism of pulse-duration modulation. / (signal processing) Initialism of pulse-density modulation.

Initialism of Portable Document Format. A document in PDF format. / Alternative letter-case form of pdf (“probability density function”) / Abbreviation of people's defence force.

Initialism of Portable Document Format. A standard for representing electronic documents, allowing them to be transmitted and reproduced accurately with the same printed layout.

Initialism of preliminary design review.

Initialism of Physicians' Desk Reference.