Hi Sven,
I just signed up for this forum today and this is my first post. I hope I can help you out with your problem. It sounds similar to one I had.
I needed to convert a one page picture of a table that I received in pdf format into a Excel sheet. I have PDF Pen Pro but that did not do it for me. I ended up buying “PDF Converter with OCR” from the Mac App store. The developer is Enolsoft. Here is their web site.
https://www.enolsoft.com/pdf-converter-with-ocr-for-mac.html
The software currently is $24.00. Not cheap but it saved me a ton of time. The software did a very good job getting the data in the proper cells of the excel file. You will still have to use the excel spell checker, but I found the program’s OCR did a good job with a poor images and small text.
This might be just the tool you need.
Jim