FastPdfKit is available in 4 versions: Free, Basic, Plus and Extra, all availables through the public repository on github.
In the repository you'll find a sample Xcode project with many targets that you can customize based on your needs. To start you can try the static version distributed as framework (click here for project direct download) that will let you add pdf support in your applications with a single step.
With the free version you can use every FastPdfKit features for an unlimited period. The single limitation is a Splash Screen with FastPdfKit logo when you open every publication. You can obviously use this version to distribute applications on the App Store, no limits.
Here you can compare different commercial licenses.
Download directly the latest available version.
Or use github at best, look for updates, clone the repository or fork it to contribute to the development.