Make them manually,
find them from vendor, like
buy them from someone else
buy a tool that makes them for you e.g. pcb matrix lp wizard
In reply to eephillip:
This seems strange to me. How can a company have a product but not supply a key component of the program? Because there are no footprints in majority of the packages, I can't export a netlist to view my circuit in Allegro PCB Editor.
In reply to twill07:
Library management is one of the most important facets of PCB design. Accordingly, there are many ways of creating symbols and conventions. Many end IC vendors will have a different footprint for the same package type. It would be impossible for EDA vendor to keep track of all these variations. A library is also a marketable item. Each company generally has a librarian that has developed a system that works for that company. Cadence does provide a basic library that you can modify as you desire.
Ron Scott CID+
It sounds like you want the schematic symbol's footprint property should match a library name in Allegro?
Cadence ships with a fairly extensive schematic library with Capture (OrCAD) or Concept. Also, when you install Allegro you will get all of the Cadence footprints. Your job is to match the symbol with the footprint.
As the others have said, it's your job to make sure it all matches.