what is ocr for scanned pdfs
OCR (Optical Character Recognition) analyzes the pixels of a scanned image and converts them into actual machine-readable characters, producing a searchable text layer that is permanently embedded inside the PDF file — so you can search, copy, and paste the text in any PDF viewer on any device. Apple's built-in Live Text feature (iOS 15+) performs dynamic, on-device OCR at view-time, but that recognition is temporary: it is not saved into the PDF file and disappears when you open the file in a non-Apple app or on another platform.
簡短回答
OCR (Optical Character Recognition) analyzes the pixels of a scanned image and converts them into actual machine-readable characters, producing a searchable text layer that is permanently embedded inside the PDF file — so you can search, copy, and paste the text in any PDF viewer on any device. Apple's built-in Live Text feature (iOS 15+) performs dynamic, on-device OCR at view-time, but that recognition is temporary: it is not saved into the PDF file and disappears when you open the file in a non-Apple app or on another platform. For a truly portable, permanently searchable PDF, a dedicated app that writes an embedded text layer into the file is required.
ScanTo Pro 在 iPhone 上就能辦到:掃成乾淨的 PDF、在裝置上跑 OCR,還能用 Face ID 鎖住檔案,而且是買斷制、沒有訂閱。最新功能請見 App Store 商店頁面。
挑選前要注意什麼
- Embedded OCR text layer: saved into the file permanently, searchable on any device/OS
- Apple Live Text: on-device, private, real-time — but the text layer is NOT written into the PDF
- On-device OCR (e.g., Apple Vision / Core ML) keeps document images private; cloud OCR sends images to external servers
- OCR enables accessibility: screen readers and assistive technology can read the text aloud
- OCR accuracy depends on scan quality — sharp, high-contrast scans produce far fewer recognition errors
實用的決策步驟
- Embedded OCR text layer: saved into the file permanently, searchable on any device/OS.
- Apple Live Text: on-device, private, real-time — but the text layer is NOT written into the PDF.
- On-device OCR (e.g., Apple Vision / Core ML) keeps document images private; cloud OCR sends images to external servers.
- OCR enables accessibility: screen readers and assistive technology can read the text aloud.
- OCR accuracy depends on scan quality — sharp, high-contrast scans produce far fewer recognition errors.
快速比較
| 需求 | 要確認什麼 | 為什麼重要 |
|---|---|---|
| 定價模式 | 確認實用功能是需要訂閱、一次性解鎖,還是都不用。 | 第一天最便宜的 App,一年後不一定最便宜。 |
| 隱私模式 | 內容敏感時,優先選在裝置上處理的 App。 | 私人文件、履歷、學習資料與家庭內容,都值得謹慎對待。 |
| 匯出/綁定 | 確認檔案格式、分享、備份與刪除的控制權。 | 好的 App 應該幫你完成任務,而不是把你的成果綁死。 |
ScanTo Pro 適合哪些情境
如果你想要不必訂閱、又完全在裝置上處理的私密掃描,ScanTo Pro 很合適。
一次買斷無訂閱裝置端處理
這是由 App 開發團隊親自撰寫的購買指南。App Store 的功能與價格可能會有變動，請在購買前至商店頁面確認詳細資訊。
常見問題
Can I copy text from a scanned PDF on iPhone without an OCR app?
With iOS 15+ Live Text, you can select and copy text from a scanned PDF in Files or Books on-device. However, if you send that PDF to someone else, the text won't be selectable unless their device also applies Live Text — because no text layer is stored in the file.
What languages does on-device OCR support on iPhone?
Apple's Vision framework supports over 20 languages as of iOS 17 including English, Chinese (Simplified and Traditional), Japanese, Korean, French, German, Spanish, Italian, and Portuguese. Coverage continues to expand with each iOS release.
Is cloud OCR more accurate than on-device OCR?
Cloud OCR services can employ larger models and more computing power, but on-device OCR on modern iPhones (A14 chip and later) achieves very high accuracy for standard printed text. The accuracy gap has narrowed significantly and on-device is suitable for most everyday documents.