OCR PDF

OCR — Optical Character Recognition — is the process of converting an image of text into actual text data. A scanned document is just a picture; to a computer, the words "Invoice #1234" on a scan are nothing more than a pattern of pixels. OCR recognizes those pixel patterns as letters, reconstructs them into words, and writes a hidden text layer behind the original image. Visually nothing changes, but now Ctrl+F works, copy-paste works, and search engines can index the document.

SwitchPDF runs Tesseract — the OCR engine maintained by Google and used in countless production systems. We feed each PDF page (or image file) into Tesseract with the language pack you selected, collect the recognized text together with each word's position on the page, and produce a new PDF where the original image stays on top and an invisible text overlay sits underneath. This is the same format Adobe Acrobat produces and is universally compatible.

OCR accuracy depends almost entirely on input quality. A clean, 300-DPI scan of printed text in a single column achieves 99%+ accuracy. Faxed receipts, faded photocopies, handwriting, and exotic fonts can drop to 70–85%. Choosing the right language pack matters: running English OCR on a French document degrades accuracy significantly because the character probabilities are wrong.

Common use cases: making old scanned contracts searchable, extracting data from receipts for expense tracking, indexing historical archives, or preparing PDFs for translation (which needs real text, not images).