This is exactly why format choice matters more than people realize. PDF is a presentation layer where AI has to reconstruct meaning from a visual snapshot. A .docx file gives models structured, semantic content from the start: clean headings, real tables, actual metadata. At Microsoft Word we think about this deeply in that Copilot works with the document structure, not against it. The lesson here isn't just "compress your PDFs"... it's that the file format is part of your AI workflow.