At least 3 business days and up to a maximum of 60 days prior to the marriage ceremony. In some counties there is a basic three-business-day waiting period for issuance of the actual license.
Other counties will issue the license right away, but it will not "mature," or become valid until three days have passed.
When to Apply
You can apply through the Office of the Clerk of Oprhans' Court of any county in PA. You do not have to obtain your license in the county in which you live or are getting married. However, at busy times of the year (think April-June & August-October) some counties will prioritize, or even restrict service to residents of that county.
Where to apply
PA Marriage License Application