How to make a scanned PDF searchable with OCR

To make a scanned PDF searchable, run OCR on the PDF. OCR reads the words in each page image and adds an invisible layer of real text behind the picture, so you can search, select and copy it. The page looks exactly the same, but now your phone knows what it says.

What is OCR?

OCR stands for optical character recognition. It is software that looks at an image of text and works out which letters and words it contains. When you OCR a PDF, the result is usually a "searchable PDF": the original scan is kept as the visible page, and the recognised text sits underneath it, lined up with the words you see.

Without OCR, a scanned PDF is just a stack of photos. You can read it with your eyes, but:

• searching for a word finds nothing;
• you cannot copy a paragraph into an email;
• a screen reader cannot read it aloud;
• AI tools and file search cannot understand it.

How to tell if your PDF needs OCR

Open the PDF and try to select a word by long-pressing it. If the text highlights, the PDF already has a text layer. If nothing selects, or the whole page highlights like an image, it is a scan and needs OCR.

Another quick test is to use the search function and type a word you can clearly see on the page. If the search finds no matches, the PDF has no text layer yet.

How to OCR a PDF on your phone

1. Open your OCR tool and choose the scanned PDF.
2. Pick the language of the document, if the tool asks. This helps it recognise accents and scripts correctly.
3. Start recognition. Long documents take longer, because every page is read in turn.
4. Save the searchable PDF as a new file.
5. Test it by searching for a word or two you can see on the page.

How accurate is OCR?

On a clean, flat, well-lit scan of printed text, OCR is usually very accurate. Accuracy drops with:

• blurry or tilted photos;
• low contrast, such as faint grey text on yellowed paper;
• unusual fonts, very small print or heavy stamps over text;
• handwriting, which is much harder than print;
• tables with tightly packed columns.

The best way to improve OCR is to improve the scan. Good light, a flat page and a black-and-white filter help a lot. Our phone scanning tips explain how.

Check the important details by hand

OCR can misread similar characters, such as 0 and O, 1 and l, or 5 and S. For most searches that does not matter. For numbers that do matter, such as account numbers, amounts and dates, always check against the image before you rely on the text.

What you can do once a PDF is searchable

• Search inside it for a name, a clause or an amount. See how to search for a word inside a PDF.
• Copy text into an email, a message or a note.
• Extract all the text to a plain .txt file. The PDF to text guide covers this.
• Ask questions about it with an AI tool that can now read the words. See how to summarise a PDF and ask it questions.
• Convert it to an editable format with better results.

Does OCR change the way my PDF looks?

A good OCR process keeps the original page image, so the PDF looks the same. The file may become a little larger, because it now contains text as well as images. Some tools also produce a plain-text version, which looks different but is far smaller.

Privacy: where does the OCR happen?

Some OCR services upload your scan to a server to process it. That is a real concern for contracts, medical letters and bank statements. On-device OCR reads the page on your phone, so the document never leaves it. If the document is private, prefer that option.

Running OCR with PDF Burrow

In PDF Burrow, Make Searchable (OCR) turns scanned pages into selectable, searchable text on your device, so the file is not uploaded. Once the PDF has text, you can use Search in PDF to find words, PDF to Text to pull all the text out, or Ask AI for on-device summaries and answers.

Frequently asked questions

Can OCR read handwriting?

It can read neat handwriting to some degree, but results are much less reliable than for print. Expect to correct mistakes if you OCR handwritten notes.

Can OCR read languages other than English?

Many OCR tools support several languages and scripts. Choosing the right language before you start, where the tool offers it, gives noticeably better results.

Should I OCR a PDF that already has text?

No. If you can already select and search the text, OCR adds nothing useful and may create duplicate text. Only run it on scanned or photographed pages.

Why does OCR get some words wrong?

Blur, low contrast, small print and stamps over text all confuse it. Rescanning the page in better light usually fixes most errors.