OCR scanned PDFs without uploading
Scanned PDFs are essentially images — the text is not selectable or searchable. OCR (Optical Character Recognition) fixes this by extracting the text content. Most OCR tools require uploading your scan to a server for processing. Silent Editor runs Tesseract — the industry-standard OCR engine — entirely in your browser using WebAssembly. Your scanned documents are processed on your device, and the extracted text never touches a server.
Why OCR should run locally for scanned documents
Scanned PDFs often contain some of the most sensitive documents people handle — old legal records, medical forms, handwritten notes, historical archives, and identification documents. Uploading scans to cloud OCR services creates significant privacy exposure.
- Scanned legal documents (depositions, court records, contracts) contain privileged and confidential content.
- Medical scans (prescriptions, lab results, referral letters) are protected by HIPAA and equivalent regulations.
- Financial scans (receipts, bank statements, tax forms) contain personal financial data.
- Identity documents (passports, licenses, IDs) should never be uploaded to third-party services unnecessarily.
- Historical and archival scans may contain unpublished research, rare manuscripts, or culturally sensitive material.
How browser-based OCR works
Silent Editor uses Tesseract OCR compiled to WebAssembly (WASM), running the same proven text recognition engine used by Google Books and major digitization projects — but executing entirely on your device.
- Tesseract WASM is loaded when you open the editor, then runs without any server connection.
- Each scanned page is analyzed to detect text regions, character shapes, and word boundaries.
- Recognized text is overlaid as selectable spans on top of the scanned page image.
- You can review, correct, and edit the OCR results before exporting.
- The entire process — from scan analysis to text extraction — happens in your browser runtime.
How to OCR a scanned PDF step by step
The OCR workflow integrates directly into the editing experience — there is no separate OCR-first step.
- Step 1: Open the editor and load your scanned PDF.
- Step 2: Activate the OCR tool from the toolbar.
- Step 3: The editor analyzes each page and extracts text regions.
- Step 4: Review the extracted text overlaid on your scanned pages.
- Step 5: Edit, add annotations, or place signatures as needed.
- Step 6: Export the enhanced document with selectable text included.
Who needs local OCR
Local OCR is not just a privacy feature — it is a practical necessity for many professionals and use cases.
- Lawyers digitizing scanned depositions, contracts, and court records for case management.
- Archivists and librarians processing historical documents that should not be uploaded to commercial services.
- Healthcare administrators extracting text from scanned patient forms for record-keeping.
- Researchers making scanned academic papers searchable and quotable.
- Accountants processing scanned receipts, invoices, and financial records.
- Students making scanned textbook pages and lecture handouts searchable.
FAQ
- How accurate is the browser-based OCR?
- Tesseract is the same engine used for Google Books digitization. Accuracy depends on scan quality — clear, high-resolution scans produce excellent results. Low-quality or handwritten text will be less accurate.
- Can I OCR a PDF with mixed typed and scanned pages?
- Yes. The editor handles both native text pages and scanned (image-based) pages. OCR is applied to scanned content while native text is extracted directly.
- Does OCR work offline?
- Yes. After the editor loads, OCR processing uses Tesseract WASM running locally. No internet connection is needed for text extraction.
- What languages does the OCR support?
- Tesseract supports over 100 languages. Language data files are loaded as needed for text recognition.