Maybe just put the scanned pdfs into a hierarchical folder system, then keep a text file at the root with comma or tab-separated location, ISO date and keywords

Maybe just put the scanned pdfs into a hierarchical folder system, then keep a text file at the root with comma or tab-separated location, ISO date and keywords. Then your documents are a grep away. Maybe awk to find documents from a date range? Maybe someone clever could automate this with the OCR output...