I tested the tool, I make with iText for Khmer render on PDF in my post of http://ask.osify.com/qa/613 which is using Khmer OS Battambang to generate the PDF.
I tested on two URLs:
1. http://KhmerOCR.org by providing the image file
2. http://rnd.niptict.edu.kh/ocr/ by uploading the PDF file
Here is the result so far