Design a document processing pipeline.

Focus on outlining the key components of a document processing pipeline, including data ingestion, preprocessing, extraction, and output. Consider the types of documents you will be processing and the specific requirements for each stage, such as OCR for scanned documents or NLP for text extraction. Discuss how you would handle different formats (PDFs, images, etc.) and ensure scalability and reliability in your design. Be prepared to address potential challenges, such as data quality issues and error handling, and think about how to incorporate feedback loops for continuous improvement.