Have you tried image to LaTeX translation? It works fairly well already for text plus equations.
I've done this for a 30-page manuscript with no sources, and I was able to recreate the entire document with minimal manual intervention to get a correct PDF.
This is not programming, it's OCR and translation to a very simple markup language. It's a very easy mechanical task.
“It’s probably not hard…” - how many such wishful thinking statements were uttered by humanity.