Scanned PDFs (text recognition)

In the Zotero edition, Rectoly reads the text of scanned pages on your device, so you can search and highlight them. Nothing is sent anywhere, and the PDF itself is not changed.

Applies to Zotero edition Windows · Mac · iPad Partly included in the purchase

This page is only about the Zotero edition.

Which apps recognize scanned text

Only the Zotero edition recognizes scanned text — on iPad, Mac and Windows.

The Mendeley edition does not recognize scanned text. In a scanned PDF without a text layer, search and text selection find nothing; you can still use area highlights, sticky notes and handwriting.

Text recognition is free. Creating highlights on the recognized text is included in the purchase, like any other highlight. See Trial and purchase.

How it works

  1. Open a scanned paper. Recognition starts by itself, and you see "Recognizing text on scanned pages…".
  2. When it is done you see "Scanned text recognized".
  3. Search in the paper now finds the recognized text too ("Recognized text" with the number of matches). See Search.

Recognition runs on your device: on iPad and Mac with Apple's built-in text recognition, and on Windows with the text recognition built into Windows.

Highlight scanned text

  • Mac · iPadChoose the HL Pen and trace over the text. If recognition is still running, you are asked to trace again in a moment.
  • WindowsDrag with the mouse to select text on the scanned page (double-click for a word, Shift+click to extend). Then choose Highlight or Underline as usual.

See Highlights, underlines and areas.

Settings on Windows

  • WindowsSettings › Reader › Scanned PDFs:
    • Recognize text on scanned pages (on by default). If it is off, a paper with scanned pages tells you so and offers Turn on.
    • The text recognition languages installed in Windows, and which of them Rectoly uses to read papers.
    • Check again and Open Windows language settings.
    • Scanned text cache with Clear: the stored text is recognized again the next time each paper opens.

Add a recognition language on Windows

WindowsWindows recognizes only the languages whose text recognition is installed. If a language is missing, the paper shows "This paper has scanned pages, but Windows has no text recognition language installed." with a Windows settings button.

  1. WindowsPress Windows settings (or Open Windows language settings in Settings › Reader › Scanned PDFs).
  2. WindowsIn Windows Settings › Time & language › Language & region, add the language. If it is already there, open its Language options.
  3. WindowsInstall its optional features, including optical character recognition.
  4. WindowsBack in Rectoly, press Check again.

Clear the recognized text

Recognized text is kept on the device so a paper is only read once. To recognize everything again:

  • Mac · iPadSettings › Troubleshooting › Scanned text cache.
  • WindowsSettings › Reader › Scanned PDFs › Scanned text cache › Clear.

Limits

  • Mac · iPadRecognition is used for search and highlighting in the PDF view, not in Reading Mode.
  • Mac · iPadVertical Japanese text is not recognized.
  • Mac · iPadThere are no selection handles on recognized text; use the HL Pen.
  • Mac · iPadA search match must be within one line.

Updated September 20, 2026