Prepare a Scanned PDF for OCR
OCR reads text best from clean, high-contrast pages. If your scan has a grey background, speckles or faint letters, cleaning it up first can reduce recognition errors. Then run OCR on the enhanced file.
How to Prepare a Scan for OCR
- Open Enhance PDF Add the scanned PDF and look at the page with the smallest text.
- Clean the page Use Noise Reduction against specks and raise Contrast so letters stand out from the background.
- Convert to black and white For plain text pages, the Threshold slider gives OCR clear black letters on white.
- Run OCR Download the enhanced PDF and open it in OCR PDF to add searchable text.
Tips for Better Recognition
Do not over-sharpen
Halos around letters can confuse OCR. Moderate sharpness is enough.
Watch thin strokes
Too high a threshold breaks thin letters apart; too low fills them in. Check small text in the preview.
Straight pages
Rotate sideways pages first – in Rotate PDF or with the rotation control.
Clean scans need nothing
If the scan is already crisp and white, skip enhancement and run OCR directly.
Pages become images
The enhanced file contains page images only – that is fine, because OCR adds a new text layer afterwards.
Your file stays on your device
Enhance PDF works in your browser; your document is not uploaded to our server.
Good to Know
- OCR results always need proofreading, especially numbers, names and tables.
- Enhancement cannot recover text that is missing or completely unreadable in the scan.
Preparing Scans for OCR – Frequently Asked Questions
Does enhancement always improve OCR?
Not always. It helps with grey, noisy or faint scans. Clean scans are best left as they are.
Which settings should I start with?
Noise Reduction, then Contrast, then Threshold for text-only pages. Avoid strong Clarity and Sharpness.
Can I convert the result to Word?
Yes – run OCR first, or use Convert Scanned PDF to Word.
What resolution does the enhanced file have?
Pages are saved at 200 DPI, which is enough for OCR of normal text sizes.
Is my file uploaded to a server?
No. Enhance PDF works in your browser, so the file never leaves your device.
Is it free?
Yes – no sign-up, no watermark and no limit on the number of files.
Get Cleaner Pages for OCR
Clean up scanned pages in your browser, then make them searchable.
Clean Up Scan