Most people think OCR is a magic wand. You scan a document, click a button, and suddenly you have searchable text. It is a lie. If you are relying on standard cloud-based OCR engines for high-stakes data extraction, you are likely inheriting a 15% error rate that will haunt your database for years.
The invisible curse of bad character encoding
I have seen entire legal cases delayed because a PDF was encoded with non-standard CIDFont mappings. When you copy-paste from these documents, the text looks fine on the screen but turns into gibberish in your clipboard. This happens because the underlying ToUnicode CMap is either corrupted or missing entirely.
If you are a developer, stop trusting the visual layer. You need to be auditing the Xref tables and font descriptors. I found that stripping the embedded font and forcing a re-index using Tesseract with a custom dictionary is the only way to ensure the data is actually usable for machine learning.
Stop relying on auto-deskew features
Standard PDF converters love to brag about auto-deskewing. They claim it straightens your scanned pages perfectly. In reality, these algorithms often introduce micro-distortions in the vector paths. For a casual reader, a 0.5-degree tilt does not matter. For a firm trying to perform precise Coordinate-based Data Extraction, that tiny shift renders your localized search patterns useless.
