What Is OCR and Why Do Scanned PDFs Need It?
OCR adds machine-readable text to image-only documents. Review recognition errors and then check structure, reading order and alternatives before publication.
Optical character recognition converts images of text into machine-readable text. An image-only PDF may lack the text a document reader needs, though some assistive tools can perform their own recognition. That workaround does not make the source document accessible.
Inspect the input
Try selecting or extracting text and inspect the result. A failed selection can have causes besides scanning, including permissions or encoding problems. An existing text layer can also contain recognition errors. Determine the actual file condition before choosing OCR.
Use suitable recognition settings
Resolution, scan quality, language, fonts, skew and layout affect recognition. Follow the OCR engine's current guidance and test representative pages. Tesseract's guidance discusses input quality; it does not establish a universal 98–99% accuracy or a PDF/UA-mandated DPI rule.
Correct the recognized text
Compare the text with the page image. Check names, numbers, punctuation, equations and reading sequence. Low-quality scans, handwriting and complex notation may require rescan, specialist transcription or recreation from source.
Add and evaluate structure
A searchable layer is not the same as semantic headings, lists, table relationships or meaningful image alternatives. Tag and structure the document appropriately, then inspect the actual saved file and intended tasks. OCR alone does not establish PDF/UA or WCAG conformance.
For a large collection, inventory image-only files, retain originals and evaluate a bounded batch. Include recognition corrections, structural work, review and failures in the time estimate.
Aelira Core is beta software. Supported workflows can apply eligible partial fixes and record outcomes, but some inputs need manual work or cannot produce a downloadable remediated file. Review the actual saved output, unresolved findings and content preservation before publication. Automated scores describe implemented checks rather than accessibility conformance. Inspect the public source and release documentation and evaluate a representative authorized sample before planning a rollout.
Aelira Team
•Accessibility EngineersThe Aelira team is building beta accessibility tools for higher education. Institutions can evaluate selected checks and partial fixes on their own files, with human review required before publication.
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