Black box problems with viewing invisible text layer

Thanks @Abambo appreciate you giving it a try.

One thing I didn't mention was that this PDF was created by ScanSnap, which is the scanner software used with a Fujitsu ix500 scanner. I've made an interesting discovery. What I believe is happening is that this software creates this OCR text layer uses a glyphless font. I use that 'layer' term loosely, it's not actually a layer, because my weak understanding is that PDF's don't support layers beyond what's called optional content groups). It's just text present on the page with opacity set to zero.

A glyphless font is one that does not have an actual associated rendered image for each character. How this works exactly, I do not know, but I'm pretty sure Acrobat simply cannot render it, because, well, there's nothing to render. I discovered just now, however, is that if you do a more tools....preflight....make ocr layer, and then EDIT those blackboxes, is that if you change the font on the black boxes, lo and behold, it renders. It renders upside down. If I copy/paste the image into Photoshop, and do an Image...Image Rotation....Flip Canvas Vertical, it reads just fine.

This problem affects more than just ScanSnap'd created PDFs. Tesseract, the popular open source OCR package, also uses these fonts for the OCR layer.

I think my practical solution to this is to generate the OCR layer in a different fashion. I'm using some custom code with Python and PyMuPDF to render the PDF pages. I can pick my font used in that case.

I'm just surprised more people haven't run into this, or perhaps my google fu skills need sharpening.... Now that I know the reason, maybe a more targeted search would produce better solutions....

Thanks