Added new kb article fix-invalid-license-watermark-and-framework-mismatch-telerik-document-processing (#685)

* Added new kb article fix-invalid-license-watermark-and-framework-mismatch-telerik-document-processing

* Update fix-invalid-license-watermark-and-framework-mismatch-telerik-document-processing.md

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Co-authored-by: KB Bot <kb-bot@telerik.com>
Co-authored-by: Desislava Yordanova <dyordano@progress.com>

Author: 3 people

knowledge-base/fix-invalid-license-watermark-and-framework-mismatch-telerik-document-processing.md

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+---
+title: Handling 'Telerik.Licensing.EvidenceAttribute is not defined' Error
+description: Troubleshoot the "Invalid License" watermark in PDFs generated using Telerik Document Processing and resolve related build errors.
+type: troubleshooting
+page_title: Handling 'Telerik.Licensing.EvidenceAttribute is not defined' Error
+meta_title: Handling 'Telerik.Licensing.EvidenceAttribute is not defined' Error
+slug: handle-telerik-licensing-evidence-attribute-not-defined-error
+tags: pdfprocessing, telerik document processing, licensing, framework, error,evidence, attribute
+res_type: kb
+ticketid: 1704877
+---
+
+## Environment
+
+| Version | Product | Author | 
+| ---- | ---- | ---- | 
+| 2025.4.1104| Telerik Document Processing|[Desislava Yordanova](https://www.telerik.com/blogs/author/desislava-yordanova)| 
+|Target Framework|.NET Framework|-|
+
+## Description
+
+It is possible to observe build errors related to the `Telerik.Licensing.Runtime.dll` assembly in a .NET Framework roject, such as:
+
+- `Type 'Telerik.Licensing.EvidenceAttribute' is not defined.`
+- `warning MSB3274: The primary reference "Telerik.Licensing.Runtime, Version=1.6.5.0, Culture=neutral, PublicKeyToken=98bb5b04e55c09ef, processorArchitecture=MSIL" could not be resolved because it was built against the ".NETFramework,Version=v4.6.2" framework. This is a higher version than the currently targeted framework ".NETFramework,Version=v4.6".`
+
+## Cause
+
+Build errors indicate a mismatch between the project's target framework and the `Telerik.Licensing.Runtime.dll` reference.
+
+## Solution
+
+### Step 1: Add Telerik.Licensing.Runtime.dll Assembly Reference
+
+1. Locate the `Telerik.Licensing.Runtime.dll` file in the installation folder of the Telerik product you're using. For example:  
+   `C:\Program Files (x86)\Progress\Telerik Reporting 2025 Q4\Bin`
+2. Add a reference to this assembly in your project.
+
+### Step 2: Update Target Framework
+
+1. Open your project in Visual Studio.
+2. Right-click your project → Select `Properties`.
+3. Navigate to the `Application` tab.
+4. Change the `Target Framework` to `.NET Framework 4.6.2` or higher.
+5. Save changes and rebuild your solution.
+
+### Step 3: Verify Licensing Integration
+
+1. Ensure the license key is correctly integrated into your project as per the [Setting Up Your Telerik Document Processing Libraries License Key]({%slug setting-up-license-key%}) documentation.
+2. Place `TelerikLicense.cs` (`TelerikLicense.vb`) in the startup project and confirm that the namespace `Telerik.Licensing` is recognized.
+
+### Step 4: Rebuild Solution
+
+1. Rebuild your project after ensuring the above steps have been completed.
+2. Check if the errors and watermark are resolved.
+
+## See Also
+
+- [System Requirements]({%slug installation-system-requirements%})
+- [Setting Up Your Telerik Document Processing Libraries License Key]({%slug setting-up-license-key%})
+