You should use the PDF24 Creator if you can. This is a software for Windows and this one can create PDF/A files. Our online OCR tool is sometimes a bit busy in peak cases. We increase our workers periodically, but sometimes it comes to peaks and a lot of people use our services and then it can take time to get a result. My advise is, use the PDF24 Creator if you can.
You say it hangs. What exactly does that mean? What do you see? OCR is a time consuming task and it sometimes takes a bit longer to get your job processed. Leave the status window open and wait until processing finishes. Sometimes our OCR backend is a bit busy. All jobs are queued and we process them in order and this could take a couple of minutes. We know that there are some peaks and we will increase our worker machines in the near future.