Ruby FPDF is a Ruby port of Olivier Plathey's excellent PDF generator, FPDF. FPDF is written in PHP, and as such can only be used from PHP scripts. Ruby FPDF, as the name suggests, is written in Ruby and can be used from Ruby scripts.
Generate PDF files directly from your Smalltalk image.
Note: This library has *NOTHING* to do with Ruby, but it was the least offensive "category" in the list.
Haru is a free, cross platform, open-sourced software library for generating PDF written in ANSI-C. It can work as both a static-library (.a, .lib) and a shared-library (.so, .dll).