Quick summary: img2pdf (requires iOS 18 or later) uses Apple's native Vision framework to perform on-device OCR on your documents. It embeds a transparent text layer directly beneath your scanned images so recipients can highlight text, copy numbers, and search across pages in any standard PDF viewer — completely free and offline.

What is a searchable PDF (and how does OCR work)?

A standard scan is simply a digital photograph of a physical page. The computer or phone sees a grid of colored pixels rather than letters, words, or paragraphs.

Optical Character Recognition (OCR) analyzes the visual shapes of letters and words on the page. In a searchable PDF (also known as a PDF with hidden text), the original high-resolution scan image is kept in the foreground, while an invisible, perfectly aligned text layer is placed directly behind it.

When you open the document in Apple Preview, Adobe Acrobat, or a web browser:

  • You see the original authentic paper scan.
  • You can press Cmd+F (or tap Find in iOS) to jump to any word instantly.
  • You can click and drag to highlight paragraphs, copy quotes, or paste tables into spreadsheets.

The privacy problem with cloud-based OCR scanners

Most third-party mobile scanner apps (such as Adobe Scan, CamScanner, or online web tools) process OCR by uploading your document scans to remote server farms. This creates severe privacy concerns:

  • Confidential data exposure: Medical records, financial statements, and contracts are transmitted to cloud infrastructure.
  • Internet dependency: Cloud OCR fails entirely if you are on an airplane, in an underground office, or in an area with poor cellular reception.
  • Subscription paywalls: Apps like Scanner Pro ($29.99/year) or Adobe Scan restrict full text OCR export to paid subscription tiers.

On-device OCR with Apple Vision framework in img2pdf

img2pdf takes a privacy-first approach by utilizing Apple's native VisionKit and Vision frameworks built directly into iOS 18:

  1. 100% Local Neural Engine processing: Text recognition executes on the iPhone's dedicated hardware chips (Apple Neural Engine).
  2. Airplane Mode compatible: The app operates without an internet connection and generates zero network requests.
  3. Completely free: Zero subscriptions, zero in-app purchases, and no artificial page limits.

Step-by-step: creating a searchable PDF on iPhone

  1. Open img2pdf: Launch the app on your iPhone or iPad (requires iOS 18 or later).
  2. Scan or pick images: Tap Scan to capture physical documents with automatic border detection, or tap Choose photos to select existing camera photos or receipts.
  3. Review and edit: Drag thumbnails to arrange your pages. Tap any page to crop, rotate, or redact sensitive account numbers.
  4. Enable OCR in Export Settings: In the export sheet, switch Searchable PDF (OCR) to On.
  5. Select your preset: Choose Small (150 DPI B&W for email), Standard (200 DPI balanced color), or Best (original camera clarity).
  6. Tap Save PDF: img2pdf recognizes the text and compiles the searchable document in seconds.

Frequently Asked Questions

What is a searchable PDF?

A searchable PDF contains both the visual scan image and an underlying invisible, machine-readable text layer aligned exactly over the words. This lets you search for keywords using Find (Cmd+F), highlight phrases, and copy text directly from a photo-based scan.

Does OCR on img2pdf send my documents to an online cloud API?

No. Optical character recognition in img2pdf is powered 100% locally by Apple's native Vision framework and the Apple Neural Engine on your device. It requires no network connection and works completely in Airplane Mode.

Does compressing a scanned PDF remove text selection or OCR?

No. When using img2pdf's export presets (Small, Standard, Best) with OCR enabled, the text layer is preserved alongside the compressed images, ensuring the PDF remains searchable and selectable in any PDF viewer.

Do I have to pay a subscription to unlock OCR on img2pdf?

No. While competitors like Scanner Pro ($29.99/year) or Adobe Scan restrict OCR behind paid subscriptions, img2pdf provides on-device OCR completely free with no subscriptions or in-app purchases.

Make your document scans searchable on iPhone

100% private on-device OCR with zero cloud uploads and no subscriptions.

Download on the App Store
Requires iOS 18 or later · Universal iPhone and iPad app · Free