How to Make a Scanned PDF Searchable, Offline

What OCR does to a scanned PDF

A scanned page is only a picture of the words, so a search finds nothing on it and the mouse cannot select a line. Optical character recognition (OCR) reads the words in the picture and adds them back as an invisible layer of text, each word in exactly the place it appears.

The page looks the same as before. The difference is that the PDF now behaves like any other: you can search it, select and copy from it, and edit or redact its text.

How to OCR a scanned PDF in Monstera

1. Open the scan

   Install Monstera free from the Microsoft Store and open the scanned PDF. A page that is only a picture says so when you try to select text on it.

2. Start text recognition

   In the rail, choose Tools, then OCR pages in the OCR group. Its full name is Make scanned pages searchable.

3. Choose the language

   Under Languages of the text (up to three), tick the language of the document. If a page mixes languages, tick each of them and they are read together.

4. Choose the pages

   Choose This page or All pages, then Recognise. Progress shows in the status bar, and the Recognition window says how many pages were read.

5. Save

   Save the document, and the text layer is saved with it.

Languages Monstera can read

Monstera reads printed text in 14 languages: English, Spanish, French, German, Portuguese, Italian, Dutch, Russian, Arabic, Hebrew, Hindi, Japanese, Korean and Chinese (Simplified).

The recognition window opens with the languages you set in Settings, on the OCR page, under Recognition languages. Set your usual languages there once; choosing others in the window changes only that run.

Good to know

• Only scanned pages are read. Pages that are already mostly text are left alone, and the result tells you which. A page read a second time replaces the hidden words Monstera added before, so a search finds each word once.
• Stopping is safe. If you stop part way, the pages already done keep their text. Each page can be undone with Ctrl+Z.
• Dark, uneven or crooked scans can be tidied first with Clean up scanned pages and Straighten crooked pages.
• Handwriting is not read by OCR. Monstera reads handwriting into Excel and Word with your own Azure or Anthropic account; see Read handwriting.

What you can do once the text is read

• Search the whole document and copy text from it.
• Edit the words with Edit text. Each line you change is drawn over a patch in the paper's own colour, and the scanned picture underneath is never altered. See how to edit PDF text.
• Redact by search: find every name or number and remove it with Find and redact.
• Keep a searchable copy with Export a searchable copy.

Questions

Is my scan uploaded to do the OCR?

No. Text recognition runs on your own computer and nothing is sent anywhere, so it also works with no internet connection.

Does OCR change how the scanned page looks?

No. The recognised words are added as an invisible layer in exactly the right places. The picture stays as it was; what changes is that you can search, select and copy the text.

Which languages can Monstera OCR?

14 languages: English, Spanish, French, German, Portuguese, Italian, Dutch, Russian, Arabic, Hebrew, Hindi, Japanese, Korean and Chinese (Simplified). Up to three can be read together on a page that mixes them.

Can I edit the text after OCR?

Yes. Once the words are read, Edit text changes them like any other text. Each changed line is drawn over a patch matching the paper, and the scan underneath is kept, so nothing is lost.

Full instructions in the Help

• Make scanned pages searchable (OCR)
• Clean up scanned pages
• Save a searchable copy of a scan

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