OCRmyPDF adds an OCR text layer to scanned PDF files
A PDF processor written in Go
a graphical user interface for the PDF Toolkit (PDFtk)
PHP library generating PDF files from UTF-8 encoded HTML
This is a small PDF editor based on OpenPdf core and AndroidPdfViewer
Fast, Nimble PDF Writer for Ruby
Convert HTML to PDF using Webkit (QtWebKit)
Convert files with output for dot-matrix printer into PDF
It is a Windows library that merges standard PDFs into a final PDF
PHP class for PDF
PDF Library for Developers