Tesseract - Tesseract is an optical character recognition engine for various operating systems
PDFCrowd - Pdfcrowd is a Web/HTML to PDF online service. Convert HTML to PDF online in the browser or in your PHP, Python, Ruby, .NET, Java apps via the REST API.
ABBYY FineReader - ABBYY's latest PDF editor software, FineReader 16 you can easily convert files like PDF to Excel, PDF to Word, edit, share, collaborate & more with this PDF editor!
PDFSwitch - Convert any HTML document or URL to PDF with a single API request.
Onlineocr.net - Free Online OCR service allows you to convert PDF document to MS Word file, scanned images to editable text formats and extract text from JPEG/TIFF/BMP files
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request