When you double click PEF files on computer, the associated program will be launched to open the selected PEF file. But you can change it to any program at your pleasure.
a) Select a program to open PEF files on Windows
Right-click on the PEF file and go through 'Open with' > 'Choose default program'. In the pop-up windows, choose a program as the PEF file opener. If you decide to always open PEF files with the program, only check the option 'Always use the selected program to open this kind of file'.

b) Select another application to open PEF files on Mac
First Get Info about any one of PEF files by right-clicking or Command-I, and click 'Open with' arrow to choose a program to start your PEF file. Click 'Change All' button to set the selected application as the default PEF file opener app.

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