Most PDF parsers give you coordinate data (bounding boxes) for extracted text. Use these to draw highlights over your PDF viewer - users can then click the highlights to verify if the extraction was correct.

The tricky part is maintaining a mapping between your LLM extractions and these coordinates.

One way to do it would be with two LLM passes:

  1. First pass: Extract all important information from the PDF
  2. Second pass: "Hey LLM, find where each extraction appears in these bounded text chunks"

Not the cheapest approach since you're hitting the API twice, but it's straightforward!