Tables in PDFs for RAG: Don’t Flatten the Grid

Flattening tables in PDFs into simple text for RAG systems destroys their crucial row and column structure, causing language models to lose context and hallucinate answers. The solution is to stop treating tables as prose and instead restore them to a structured data format as early as possible. A diagnostic approach assesses each table's properties—such as its size, parse quality, and whether it spans multiple pages—to determine the best way to handle it. Based on this diagnosis, tables can be represented in four ways, from simple Markdown lines for basic queries to fully structured, typed columns in a database for complex, corpus-wide analysis.