Files with PK extension as mainly used by Syntrillum Cool Edit audio editing tool. In 2003 Abode acquired the project and rebranded it as Audition. PK file contains waveform image data for audio files opened with the program.

Files with PK extension are saved in the same folder as the corresponding audio files and are generated automatically upon importing file into the program. PK accelerate load process and allow for more streamlined and precise editing.