---
title: "Convert PDFs to searchable text in C# | Nutrient .NET SDK OCR library"
canonical_url: "https://www.nutrient.io/guides/dotnet/ocr/usage/pdf-to-searchable-pdf/"
md_url: "https://www.nutrient.io/guides/dotnet/ocr/usage/pdf-to-searchable-pdf.md"
last_updated: "2026-05-21T17:12:02.207Z"
description: "Learn how to use Nutrient .NET SDK OCR library in C# to convert PDF files into searchable and editable text, enhancing document accessibility and searchability."
---

# OCR PDF in C#

This guide demonstrates how to convert a PDF file into a searchable PDF using Nutrient.NET SDK’s powerful OCR library for C#. With our advanced optical character recognition (OCR) engine, you can extract text from PDF files and save it in a separate PDF, facilitating searchability and enabling users to copy and paste text seamlessly. This process enhances document accessibility and supports efficient text recognition in.NET applications.

## OCR all pages in one call

In addition to the page-by-page `OcrPage` workflow below, you can OCR an entire document in a single operation using `OcrPages`.

```csharp

using GdPicturePDF pdf = new GdPicturePDF();
pdf.LoadFromFile(@"input_image_based.pdf");
pdf.OcrPages("*", 0, "eng", "", "", 200);
pdf.SaveToFile(@"output.pdf");

```

This approach is useful for streamlined server workflows where you want to process all pages with one call.

## Converting PDF to searchable PDF

To convert a PDF file into a searchable PDF using Nutrient.NET SDK's OCR library, follow the steps below:

1. Create a `GdPicturePDF` object.

2. Load the source document by passing its path to the `LoadFromFile` method of the `GdPicturePDF` object.

3. Determine the number of pages with the `GetPageCount` method of the `GdPicturePDF` object.

4. Iterate through pages of the source document.

5. For each page, run the OCR process with the `OcrPage` method of the `GdPicturePDF` object. Configure the OCR process by passing the following parameters to the `OcrPage` method:
   1. **Language settings**: Set the code of the language that Nutrient.NET SDK uses to recognize text in the source document. To specify several languages, separate the language codes with the `+` character. For example, `eng+fra`.
   2. **OCR resource folder path**: Set the path to the OCR resource folder. The default language resources are located in `GdPicture.NET 14\Redist\OCR`. For more information on adding language resources, see the [language support](https://www.nutrient.io/guides/dotnet/ocr/language-support.md) guide.
   3. **Character allowlist**: Set the character allowlist. When scanning the document, the OCR engine only recognizes the characters included in the allowlist. When you set `""`, all characters are recognized.
   4. **DPI resolution**: Set the dot-per-inch (DPI) resolution the OCR engine uses. It’s recommended to use `300` for the best combination of speed and accuracy.

6. Save the result in a new PDF document.

This approach enables you to effectively integrate OCR-powered PDF-to-searchable-PDF functionality in.NET applications, improving text accessibility and usability.

The example below converts a PDF file to a searchable PDF:

### C#

```csharp

using GdPicturePDF gdpicturePDF = new GdPicturePDF();
// Load the source document.
gdpicturePDF.LoadFromFile(@"C:\temp\source.pdf");
// Determine the number of pages.
int pageCount = gdpicturePDF.GetPageCount();
// Loop through the pages of the source document.
for (int i = 1; i <= pageCount; i++)
{
    // Select a page and run the OCR process on it.
    gdpicturePDF.SelectPage(i);
    gdpicturePDF.OcrPage("eng", @"C:\GdPicture.NET 14\Redist\OCR", "", 300);
}
// Save the result in a new PDF document.
gdpicturePDF.SaveToFile(@"C:\temp\output.pdf");
gdpicturePDF.CloseDocument();

```

### VISUAL BASIC

```vb

Using gdpicturePDF As GdPicturePDF = New GdPicturePDF()
    ' Load the source document.
    gdpicturePDF.LoadFromFile("C:\temp\source.pdf")
    ' Determine the number of pages.
    Dim pageCount As Integer = gdpicturePDF.GetPageCount()
    ' Loop through the pages of the source document.
    For i = 1 To pageCount
        ' Select a page and run the OCR process on it.
        gdpicturePDF.SelectPage(i)
        gdpicturePDF.OcrPage("eng", "C:\GdPicture.NET 14\Redist\OCR", "", 300)
    Next
    ' Save the result in a new PDF document.
    gdpicturePDF.SaveToFile("C:\temp\output.pdf")
    gdpicturePDF.CloseDocument()
End Using

```

#### Used methods and properties

- [`CloseDocument`](/api/gdpicture/GdPicture.NET.14~GdPicture14.GdPicturePDF~CloseDocument.html)

- [`GetPageCount`](/api/gdpicture/GdPicture.NET.14~GdPicture14.GdPicturePDF~GetPageCount.html)

- [`LoadFromFile`](/api/gdpicture/GdPicture.NET.14~GdPicture14.GdPicturePDF~LoadFromFile.html)

- [`OcrPage`](/api/gdpicture/GdPicture.NET.14~GdPicture14.GdPicturePDF~OcrPage.html)

- [`SelectPage`](/api/gdpicture/GdPicture.NET.14~GdPicture14.GdPicturePDF~SelectPage.html)

- [`SaveToFile`](/api/gdpicture/GdPicture.NET.14~GdPicture14.GdPicturePDF~SaveToFile.html)

#### Related topics

- [Load a file](/guides/dotnet/load-a-file.md)

- [Save a file](/guides/dotnet/save-a-file.md)
---

## Related pages

- [C# barcode recognition](/guides/dotnet/ocr/usage/barcode-recognition.md)
- [C# OCR scanning to searchable PDFs](/guides/dotnet/ocr/usage/ocr-scan.md)
- [Convert images into searchable PDF/A files in C#](/guides/dotnet/ocr/usage/pdfa-archiving.md)
- [C# OCR image to text](/guides/dotnet/ocr/usage/image-to-searchable-pdf.md)