The extraction pipeline handles a wide range of document types. This article lists what's supported, with notes on accuracy and tuning per type.
High-Accuracy Document Types
- Modern PDF invoices: Text-based PDFs from common accounting systems extract reliably. 95%+ accuracy on totals, dates, supplier names.
- Passport MRZ zone: Machine-readable zone yields near-perfect extraction.
- Pre-printed forms: Fixed-layout forms with checkbox marks and known field positions.
- Modern receipts: Thermal receipts photographed in good light read well.
Variable-Accuracy Types
- Photographed receipts in low light: Wrinkled, faded or dimly lit images degrade OCR.
- Handwritten forms: Tesseract struggles; cloud OCR is significantly better but still imperfect.
- Scanned old documents: Faded ink, marginalia, stamps confuse layout analysis.
- Multi-page invoices with continuation tables: Detecting where the table continues across pages requires careful rule design.
Limited Support
- Drawings and diagrams with embedded labels.
- Heavily formatted marketing PDFs where data is artistic rather than structured.
- Languages without Latin script in default Tesseract; cloud OCR handles most.
- Encrypted documents can't be read without decryption.
Worked Examples
- Accounts payable team: Receives invoices in mixed formats. PDF-from-Word ones extract perfectly; scanned ones go to review queue.
- Employee onboarding: Passport MRZ extraction works; photo extraction works; signature page requires manual confirmation.
- Multi-language receipts: Cloud OCR with language hints for tenants in Germany, Spain, Brazil.
- Multi-page contracts: Extract counterparties from the cover page; extract signature page details from the back; review middle pages manually.