# Make a scanned PDF searchable in C#

> Add an invisible OCR text layer to scanned PDFs in .NET with the PdfNetStack.Ocr add-on, Latin and Arabic, models checked by hash. MIT.

Available since 1.1.

Read the text of scanned pages and lay it over the scans, so the PDF selects, copies and searches.

## Short answer

Load the OCR models with `OnnxOcrEngine.Load`, then call `PdfOcr.MakeSearchable` on the document and
save it. Each page's scan is found, turned upright, read, and every word is laid over it as
invisible text. The pages look the same as before.

```csharp title="recipe-make-scanned-pdf-searchable.cs"
#:package PdfNetStack.Ocr@1.2.0
using PdfNetStack;
using PdfNetStack.Ocr;

// Models: python tools/fetch_ocr_models.py models (checked against pinned SHA-256 hashes).
using var engine = OnnxOcrEngine.Load("models", new OnnxOcrEngineOptions { Languages = ["latin", "arabic"] });

PdfDocument doc = PdfDocument.Open("scan.pdf");
var ocr = new PdfOcr(engine, new PdfOcrOptions { Languages = ["latin", "arabic"] });
PdfOcrReport report = ocr.MakeSearchable(doc);   // invisible text laid over each scan
doc.Save("scan-searchable.pdf");
Console.WriteLine(report.Text);
```

## Notes

- `PdfNetStack.Ocr` is a separate package on NuGet. It runs the PP-OCRv5 mobile models on ONNX
  Runtime.
- Get the models from the `PdfNetStack.Ocr.Models` package, or with
  `python tools/fetch_ocr_models.py models`. They are checked against pinned SHA-256 hashes when
  loaded.
- A page qualifies when its scan is one image covering at least half the page. Pages that already
  have text are left alone. `Recognize` reports the text without changing the document.
- ONNX Runtime's official builds send telemetry by default. The engine turns it off before loading
  a model; on Linux and macOS also set `ORT_DISABLE_TELEMETRY=1` before the process starts.

## Related

- [OCR](https://www.jadev-corp.com/guides/ocr/)
- [Extract text](https://www.jadev-corp.com/guides/extract-text/)
- API: [PdfOcr](https://www.jadev-corp.com/api/pdfnetstack-ocr/pdfocr/), [OnnxOcrEngine](https://www.jadev-corp.com/api/pdfnetstack-ocr/onnxocrengine/)

Source: https://www.jadev-corp.com/pdfnetstack/recipes/make-scanned-pdf-searchable/