Comment by MassPikeMike

Apple Vision and its wrappers provide bounding boxes for each line of text. That's slightly less convenient than Tesseract which can give you a bounding box for each word, but more than compensated by Apple Vision's better accuracy. I am planning to fudge the word boxes by assuming fixed-width letters and dividing up the overall width so that each word's width is proportional to its share of the total letters on the line.

Once you have those bounding boxes, it's pretty simple to use a library like [1] (Python) or [2] (JavaScript) to add overlay text in the right place. For example, see how [3] does it.

[1] https://pymupdf.readthedocs.io/en/latest/recipes-text.html#h... [2] https://github.com/foliojs/pdfkit [3] https://github.com/eloops/hocr2pdf