Comment formater un numéro de téléphone

Assuming you're talking about a text field in a PDF, you can use the built-in Phone Number option under Properties - Format - Special.

However, this uses the American standard for phone numbers. If you use a different one then you can use the Arbitrary Mask option, like this (for example):

(99) 999-9999

If the user then enters "123456789" it will automatically appear as "(12) 345-6789".