Tesseract
Free software for OCR (optical character recognition). See https://github.com/tesseract-ocr .
sudo apt install tesseract-ocr
NB you need to install the language specific package for whatever language text you are trying to convert. Tesseract languages are identified by three letter codes like "eng" (for english, the default).
sudo apt install tesseract-eng
For instance for converting Dutch language documents:
sudo apt install tesseract-ocr-nld