print/pdflib: License allows distribution

Add LICENSE and details.
There is no need for this port to be restricted- it is freely
redistributable.

https://lists.freebsd.org/pipermail/freebsd-ports/2021-March/120412.html

While here, a few style fixes and updates

Reported by: Patrick M. Hausen <hausen@punkt.de>
Approved by: maintainer timeout (ale, >14 days)
Differential Revision: https://reviews.freebsd.org/D29059