I have written a small wrapper for Abbyy OCR4LINUX CLI engine (IMHO, doesn't cost that much) and Tesseract 3.
The wrapper can batch convert files like:
$ pmocr.sh --batch --target=pdf --skip-txt-pdf /some/directory
The script uses pdffonts to determine if a PDF file has already been OCRed to skip them. Also, the script can work as system service to monitor a directory and launch an OCR action as soon as a file enters the directory.
Script can be found here:
https://github.com/deajan/pmOCR
Hopefully, this helps someone.
