> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/uwp/low-level-pdf-api/add-custom.md).

# Information dictionary: adding custom data to a PDF in UWP

Learn how to add custom data to PDF files using the Cos/SDF low-level API with a full code sample. Edit existing documents easily with this step-by-step guide! The Apryse uwp SDK streamlines secure do

To add custom data to an existing document.

{% tabs %}
{% tab title="C#" %}
{% code lineNumbers="true" %}

```csharp
// In case you have PDFDoc you can always access
// SDF/Cos document using PDFDoc.GetSDFDoc() method
SDFDoc doc = new SDFDoc(filename);
Obj trailer = doc.GetTrailer();	// Get the trailer

// Create an Info dictionary
Obj info = trailer.PutDict("Info");
info.PutString("Producer", "Apryse PDFNet");

// Create a custom inline dictionary within Info dictionary
Obj custom_dict = info.PutDict("My Direct Dict");
custom_dict.PutNumber("My Number", 100);
```

{% endcode %}
{% endtab %}
{% endtabs %}

[Cos/SDF low-level API to edit PDF files](/uwp/get-started/samples.md#sdf) Full code sample which illustrates how to use basic Cos/SDF API to edit an existing document.


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