How to prepare a scan for accurate OCR

When to use it

OCR quality depends on orientation, skew, sharpness, contrast, language and page structure. Preparing a scan reduces uncertain words and shortens manual review. The situations below show when this guide can help you choose the right workflow and avoid unnecessary processing.

• Pages are skewed, rotated or surrounded by wide dark margins.
• A previous OCR run produced many errors in ordinary printed text.

How it works

This guide divides the topic into three consecutive stages: correct orientation, clean the frame, configure ocr. Follow them in order to understand the result and the points that require manual review.

1. 01Correct orientationRotate pages to their normal position and distinguish a 90-degree rotation from a small skew in text lines.
2. 02Clean the frameRemove unnecessary margins without losing content, then review contrast, sharpness and consistent scale across pages.
3. 03Configure OCRChoose languages, limit processing to required pages and identify areas containing tables or small text.

What changes

Before starting, identify which parts of the document will change and which will remain intact. The list below describes changes in the output copy rather than hidden modifications to the source file.

• Page orientation and geometry become more predictable.
• OCR receives less background noise and straighter lines for segmentation.
• The prepared PDF is saved as a separate copy before recognition.

What can be lost

Some operations affect more than the visible page and can change text layers, forms, links or signatures. This list helps you decide whether the separate output copy is suitable for the next stage of your work.

• Aggressive cropping can remove page numbers, signatures or margin notes.
• Heavy thresholding can lose thin strokes and punctuation marks.

Limitations

Limitations describe the current implementation boundary and the cases that require additional review. Check them before uploading, especially when a document is complex, protected or contains important structure.

• Very low resolution cannot be fully corrected by software processing.
• Strong shadows, glare and complex backgrounds may remain after basic correction.
• Handwriting, formulas and dense tables require extended manual review.

Related tools

Related tools let you move directly from the explanation to the appropriate action. Each tool uses its own workflow and shows its specific limits before processing starts.