How to OCR a PDF for Free: Make Scanned Documents Searchable

Quick summary: To OCR a PDF for free, upload it to Google Drive and open it with Google Docs — Google runs OCR automatically and the text becomes copyable. On Mac, Preview applies basic OCR to scanned PDFs when you use Edit → Select All. For full OCR with a searchable PDF output, use Tesseract (free, command line) or a free online OCR tool.

OCR stands for Optical Character Recognition — the process of reading text from an image and converting it into real, editable, searchable characters. A scanned PDF is an image; after OCR, it becomes a proper text document where you can search with Ctrl+F, copy passages, and use screen readers. You can also upload the OCR’d result to our free AI PDF reader to summarize it or ask questions about the content.

What is OCR and when do you need it?

You need OCR when:

• Your PDF was created by scanning a paper document.
• You open the PDF and cannot select or copy any text.
• Ctrl+F finds nothing even though you can see words on the page.
• A screen reader cannot read the document aloud.

A text-based PDF (exported from Word, Google Docs, or any software) already has a text layer — you do not need OCR for those.

How to check: Open the PDF, press Ctrl+A (select all). If text highlights, it is already a text PDF. If nothing happens or only images select, it is a scanned PDF that needs OCR.

How to OCR a PDF for free with Google Drive (no install)

Google Drive runs OCR automatically when you open a PDF with Google Docs — completely free:

1. Go to drive.google.com and sign in with your Google account.
2. Click ”+ New” → File upload and upload your scanned PDF.
3. Right-click the uploaded PDF → “Open with” → “Google Docs”.
4. Google converts the PDF and runs OCR. The text appears as editable content in a new Google Doc.
5. To get a searchable PDF back: File → Download → PDF Document.

Accuracy: Google’s OCR is excellent for clean, typed text in English and most European languages. Handwriting, very small text, and unusual fonts may have errors.

Limitation: Complex layouts (multi-column, tables, graphics) may lose their structure in the Google Doc. The text is there, but formatting may be messy.

How to OCR a PDF on Mac

Method 1: Preview (basic, built-in)

Preview applies lightweight OCR to scanned PDFs automatically in macOS 10.15 (Catalina) and later:

1. Open the scanned PDF in Preview.
2. Press Cmd + A to select all. If text highlights, Preview has already recognized it.
3. You can now search with Cmd + F and copy text with Cmd + C.

Preview does not create a new “searchable PDF” file — it shows you the recognized text in the viewer but does not save a text layer back to the file. To get a proper searchable PDF, use one of the other methods below.

Method 2: Tesseract (free, command line)

Tesseract is the best free OCR engine. Install it via Homebrew:

brew install tesseract

Convert the PDF to images first (one image per page), then run OCR:

# Step 1: Convert PDF pages to PNG images
gs -sDEVICE=png16m -r300 -sOutputFile=page-%d.png -dNOPAUSE -dBATCH input.pdf

# Step 2: OCR each image to create searchable PDFs
for img in page-*.png; do
  tesseract "$img" "${img%.png}" pdf
done

# Step 3: Merge the page PDFs (requires pdftk)
pdftk page-*.pdf cat output searchable.pdf

This produces a proper PDF with an invisible text layer behind the original image — the document looks identical but is now fully searchable.

How to OCR a PDF on Windows

Method 1: Google Drive (see above)

Works the same on Windows — upload, open with Google Docs, download.

Method 2: Tesseract for Windows

Download the Tesseract installer for Windows from the UB Mannheim GitHub release page. After installation:

tesseract input.tiff output pdf

You need to convert PDF pages to TIFF or PNG first. Use Ghostscript (also free) for the conversion:

gs -sDEVICE=tiffg4 -r300 -sOutputFile=page-%d.tiff -dNOPAUSE -dBATCH input.pdf

Then run Tesseract on each .tiff file and merge the results.

Method 3: Microsoft OneNote (free with Windows)

OneNote has a hidden OCR feature:

1. Open Microsoft OneNote.
2. Insert the PDF pages as images: Insert → Pictures.
3. Right-click an image → “Copy Text from Picture”.
4. Paste the extracted text into any text editor.

This works for extracting text but does not produce a searchable PDF output.

How to OCR a PDF online (free, no install)

Several free browser-based OCR tools convert scanned PDFs into searchable files without installation. Search for “OCR PDF free online”:

1. Upload your scanned PDF.
2. Select the document language.
3. Download the searchable PDF or extracted text.

Popular options include Google Drive (described above) and several well-reviewed free web tools.

Privacy note: Online tools upload your file to a remote server. For confidential documents, use the local Tesseract method instead.

How to OCR a PDF on iPhone

There is no dedicated free OCR app built into iOS, but two options work:

Method 1: Live Text (iOS 15+)

On iOS 15 and later, tap and hold on any text in an image (including a scanned PDF open in Files or Photos) — Live Text highlights the recognized text, and you can copy it. This works page by page and does not produce a searchable PDF output.

Method 2: Notes app

1. Open the Notes app and create a new note.
2. Tap the camera icon → Scan Documents.
3. Scan the paper document (or take a photo of each page).
4. iOS automatically applies OCR — the scanned text becomes searchable within Notes.
5. Share the note as a PDF: tap the Share button → Print → pinch-out → Save to Files.

How to check OCR quality

After running OCR, verify the result:

1. Press Ctrl+F (Windows) or Cmd+F (Mac) in the PDF viewer.
2. Search for a specific word you can see on the page.
3. If it is found and highlighted, OCR succeeded.
4. Spot-check a few passages by selecting text and reading it — look for garbled characters (l vs 1, O vs 0, rn vs m).

For critical documents (legal, medical, financial), proofread the extracted text carefully before relying on it.

How to improve OCR accuracy

Factor	Recommendation
Scan resolution	300 DPI minimum; 600 DPI for small text
Image quality	Straight, flat scan — no shadows, no distortion
Language setting	Match the document language in OCR settings
Font type	Printed fonts OCR better than handwriting
Background	White background, dark ink — best contrast

Tesseract supports 100+ languages. Use tesseract --list-langs to see installed language packs, or install additional ones with Homebrew.

Frequently Asked Questions (FAQ)

What does OCR stand for?

OCR stands for Optical Character Recognition — a technology that reads text from images and converts it into machine-readable characters.

Is OCR 100% accurate?

No. Accuracy depends on the scan quality, font, language, and OCR engine. Modern engines (Google, Tesseract) achieve 95–99% accuracy on clean, high-resolution scans of standard fonts. Low-resolution scans, unusual fonts, or handwriting can drop accuracy significantly.

Can OCR read handwriting?

Standard OCR engines handle printed (typed) text reliably. Handwriting recognition (HWR) is a different problem — accuracy is much lower and depends on handwriting clarity. Google’s OCR and iOS Live Text do attempt handwriting, with mixed results.

Will OCR change the visual appearance of my PDF?

With the Tesseract searchable-PDF method, no — the original image remains, and an invisible text layer is added behind it. The PDF looks identical; it is just now searchable. Google Docs conversion changes the layout to match a word-processor document, which may look different.

How do I OCR a multi-page scanned PDF?

All the methods above handle multi-page PDFs. Tesseract processes each page image separately and you merge the results. Google Drive handles multi-page PDFs in one upload. Most online tools accept multi-page PDFs directly.

Is Tesseract really free?

Yes. Tesseract is open-source (Apache 2.0 license), maintained by Google, and free to use for any purpose including commercial.

Related guides

• PDF to text: extract text from any PDF for free — extract plain text from a PDF that already has a text layer
• How to search a PDF for free — search after making the PDF searchable
• How to copy text from a PDF for free — copy text once the PDF is OCR’d
• How to edit a PDF for free — edit the content after extracting the text
• How to convert a PDF to PowerPoint for free — convert to slides after OCR