GroupDocs.Conversion for .NET 26.9 – September 2026 Release Highlights

We’re happy to announce the release of GroupDocs.Conversion for .NET v26.9, available as of September 2026. This release introduces support for new GIS and compression formats, enables conversion of presentations to self-contained HTML slideshows, improves multi-page TIFF handling, and enforces a 10-conversion evaluation limit per process. It also removes obsolete API members and applies stricter validation for conflicting options.

What’s new in this release

• [Feature] Add WIM as a conversion source for compression documents (CONVERSIONNET-8488)
• [Feature] Add Apple Archive (AAR) as a conversion source and target for compression documents (CONVERSIONNET-8491)
• [Feature] Add ALZ as a conversion source for compression documents (CONVERSIONNET-8494)
• [Feature] Add GeoJSON Text Sequence as a conversion source for GIS documents (CONVERSIONNET-8508)
• [Feature] Add KMZ as a conversion source for GIS documents (CONVERSIONNET-8510)
• [Feature] Add GIS conversion support to the net462 target framework (CONVERSIONNET-8511)
• [Feature] Add GML and OSM XML as conversion targets for GIS documents (CONVERSIONNET-8512)
• [Feature] Convert a presentation to a self-contained HTML slideshow (CONVERSIONNET-8529)
• [Improvement] Apply each frame’s own page size and resolution when converting multi-page TIFF to PDF (CONVERSIONNET-8519)
• [Improvement] Apply the frame’s own page size and resolution when converting a multi-page TIFF page by page (CONVERSIONNET-8520)
• [Improvement] Apply each frame’s own page size and resolution when converting a multi-page TIFF to tagged PDF (CONVERSIONNET-8521)
• [Improvement] Limit evaluation mode to 10 conversions per process (CONVERSIONNET-8523)
• [Improvement] Remove the obsolete converter listener, fluent handler stages and page size properties (CONVERSIONNET-8561)
• [Bug] PPTX to PDF: double underline and double strikethrough emit NaN coordinates on Linux (CONVERSIONNET-8388)
• [Bug] Converting a PDF with more than 4 pages fails in evaluation mode (CONVERSIONNET-8515)
• [Bug] Trial pages limit is not applied when converting PDF to Web (CONVERSIONNET-8516)
• [Bug] Return the correct page count for a multi-page TIFF (CONVERSIONNET-8522)

Public API changes

Breaking changes

The members that were marked obsolete in earlier versions are removed:

In the fluent API, WithOptions(...) now returns IConversionHandlersStage (or IConversionByPageHandlersStage for page-by-page conversion). Chained calls such as .WithOptions(...).OnConversionCompleted(...).OnConversionFailed(...).Convert() compile unchanged.

Page size is now set only through SizeSettings:

var options = new CadConvertOptions
{
    SizeSettings = new PageSizeOptions { PageWidth = 800, PageHeight = 600 }
};

Evaluation-mode conversion limit

Without a valid license, a process can run at most 10 conversions. Every call to Converter.Convert(...) counts as one conversion — any overload, the fluent API, and calls that fail — regardless of how many output files it produces. Converter.GetDocumentInfo() and Converter.IsDocumentPasswordProtected() do not count. The count belongs to the running process; restarting the application starts it again. Once a valid license is applied, conversions are no longer counted or limited.

The 11th conversion throws EvaluationLimitReachedException (derived from GroupDocsConversionException) with the message:

You are using GroupDocs.Conversion in evaluation mode: the limit of 10 documents converted per process has been reached. Get a free 30-day temporary license to remove all evaluation limits: https://purchase.groupdocs.com/temporary-license/

Apply a License or a Metered key before the first conversion to remove the limit:

License license = new License();
license.SetLicense("GroupDocs.Conversion.lic");

using (Converter converter = new Converter("sample.docx"))
{
    converter.Convert("converted.pdf", new PdfConvertOptions());
}

Code that runs without a license can handle the limit:

try
{
    using (Converter converter = new Converter("sample.docx"))
    {
        converter.Convert("converted.pdf", new PdfConvertOptions());
    }
}
catch (EvaluationLimitReachedException ex)
{
    Console.WriteLine(ex.Message);
}

Slideshow output for presentation-to-HTML conversion

The new WebConvertOptions.SlideShow property (default false) converts a presentation — PPT, PPTX, PPTM, PPS, PPSX, PPSM, POT, POTX, POTM, ODP, OTP or FODP — to a single self-contained HTML file (Html or Htm) that plays as a slideshow. Existing conversions are unchanged unless SlideShow is set to true.

using (Converter converter = new Converter("presentation.pptx"))
{
    WebConvertOptions options = new WebConvertOptions { SlideShow = true };
    converter.Convert("slideshow.html", options);
}

With SlideShow = true, contradictory options throw InvalidConvertOptionsException before the conversion starts:

A slideshow is one navigable document, so the page-by-page Convert overloads throw System.NotSupportedException with the message Saving a presentation slideshow page by page is not supported.

New file types

Example converting a ZIP to Apple Archive:

using (Converter converter = new Converter("assets.zip"))
{
    CompressionConvertOptions options = new CompressionConvertOptions { Format = CompressionFileType.Aar };
    converter.Convert("assets.aar", options);
}

How to get the update

NuGet

Upgrade to the latest GroupDocs.Conversion package via NuGet: GroupDocs.Conversion 26.9.0

dotnet add package GroupDocs.Conversion --version 26.9.0

Direct download

Download assemblies from the GroupDocs.Conversion for .NET 26.9 page

Resources

• Full Release Notes
• Documentation
• Free Support Forum