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Converting Docx to PDF Throws Reference Required and RadFlowDocument is ambiguous in the namespace error


Product Progress Telerik UI for ASP.NET AJAX
Version all


I receive the following error when trying to convert a Docx file to PDF using the PdfFormatProvider:

"Reference required to assembly 'Telerik.Windows.Documents.Flow, Version, Culture=neutral, PublicKeyToken=5803cfa389c90ce7'"

After adding the reference, all commands related to Telerik.Windows.Documents.Flow gives me the following error:

"RadFlowDocument is ambiguous in the namespace 'Telerik.Windows.Documents.Flow.Model'"


"RadFlowDocument is ambiguous in the namespace 'Telerik.Windows.Documents.Flow.FormatProviders.Docx'"


To resolve the issue with the Telerik assemblies, follow these steps:

  1. Correct Document Processing Assemblies: There are two types of Document Processing assemblies – one for .NET Framework (Telerik.Windows.Documents.Flow) and another for .NET Core (Telerik.Documents.Flow). Confirm that your application references only the assemblies intended for the .NET Framework.
    • Learn from Similar Cases: A customer experiencing a similar issue found that their problem stemmed from an outdated reference, specifically Telerik.Documents.* instead of Telerik.Windows.Documents.*, with incorrect pathing. This might be worth checking in your case as well.
  2. Check for Older Assembly References: Review your web.config file for any older references to the Telerik assemblies, specifically Telerik.Web.UI.dll and the Document Processing assemblies.
  3. Examine Project Files: Open your .csproj or .vbproj files in a text editor to ensure they reference the correct versions of these assemblies.
  4. Global Assembly Cache (GAC) Verification: Search the GAC for older versions of the assemblies, which could lead to conflicts.
  5. Consistent Assembly Sources: Ensure that both Telerik.Web.UI.dll and the Document Processing assemblies originate from the same installation to avoid version mismatches.
  6. Reinstall Telerik Assemblies: If necessary, remove the Telerik assemblies and their references from the Bin folder. Then, carefully re-add them as demonstrated in the attached video tutorial.


  • Make sure to update your code where you use Telerik.Windows.Documents.Flow to match the correct assembly reference.
  • Double-check that the .NET Core assemblies are not being referenced in your project, as they can cause conflicts.
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