hexapdf (rubygems): HexaPDF is a pure Ruby library with an accompanying application for working with PDF files.  In short, it allows creating new PDF files, manipulating existing PDF files, merging multiple PDF files into one, extracting meta information, text, images and files from PDF files, securing PDF files by encrypting them and optimizing PDF files for smaller file size or other criteria.  HexaPDF was designed with ease of use and performance in mind. It uses lazy loading and lazy computing when possible and tries to produce small PDF files by default. 
Keywords: pdf|pdf-generation|pdf-manipulation|ruby