Are they? I've had excellent success. The confusing part of this is that there are two types of PDF. The first is a "normal" digital PDF. The second is a scanned PDF. The first can essentially be read like a document. LLMs have no issues with this. It's the second kind of PDF where the constraint becomes the vision capability, and this is very impressive with Astra. I've had no issues with either. I imagine there could be issues with unusually dense and/or misaligned text on scanned PDFs, but I have not tested this.

The bottom line, though, is that PDF OCR is usually regarded as a solved problem. LLMs won't usually do the recognition itself. It will farm it out to established tools which are very good.

The more data in the PDF, the more nines you need in the OCR accuracy. Plenty of 5/S, O/0 and other issues exist at frequencies that cause problems.

Well, I would argue about the first part. Even if they contain "native" text that can be extracted, in most cases their order will be messed up and it is often crucial for correct parsing.

So in many cases the visual way is the only one that works correctly, the textual one is just a shortcut that may be walkable in certain cases.

It depends on what you called solved.

If the goal is to only extract the unstructured text from the document, it is definitely solved. Extracting a more natural structure like paragraph separation, tables, header, footers (what is referred as document intelligence) is much more complicated and not fully solved, but I would say almost.