How to convert docx file to pdf using free .net library

You can use the DocumentConverter class to convert the DOCX files to PDF. Here is an example:

using (DocumentConverter documentConverter = new DocumentConverter())         
{         
   var input = @"C:\Inputfiles\input.docx");        
   var output = @"C:\Outputfiles\output.pdf");         
   var jobData = DocumentConverterJobs.CreateJobData(input, output, DocumentFormat.Pdf);         
   jobData.JobName = "pdf converter";         
        
   var documentWriter = new DocumentWriter();         
   documentConverter.SetDocumentWriterInstance(documentWriter);         
        
   var renderingEngine = new AnnWinFormsRenderingEngine();         
   documentConverter.SetAnnRenderingEngineInstance(renderingEngine);         
        
   var job = documentConverter.Jobs.CreateJob(jobData);         
   documentConverter.Jobs.RunJob(job);         
}

https://www.leadtools.com/help/sdk/v22/tutorials/dotnet-console-convert-files-with-the-document-converter.html