Convert jpg and png format images into pdf and then upload using c#

You can convert both your jpg and png format images to PDF files using the DocumentConverter. Here is some sample code that shows how you can handle this:

using (DocumentConverter documentConverter = new DocumentConverter())         
{         
   var input = @"C:\Input\input.jpg"); // supports both jpg and png     
   var output = @"C:\Output\output.pdf");         
   var jobData = DocumentConverterJobs.CreateJobData(input, output, DocumentFormat.Pdf);         
   jobData.JobName = "save to pdf";         
        
   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/tutorials/dotnet-convert-files-with-the-document-converter.html

You can use Spire.PDF (available on NuGet) to do the file format conversion.

Here is the code snippet for your reference:

//Create a pdf document with a section and page added.  
PdfDocument doc = new PdfDocument();  
PdfSection section = doc.Sections.Add();  
PdfPageBase page = doc.Pages.Add();  
//Load a png image file  
 PdfImage image = PdfImage.FromFile(@"D:\images\img.png");  
//Set image location and size in PDF  
float widthFitRate = image.PhysicalDimension.Width / page.Canvas.ClientSize.Width;  
float heightFitRate = image.PhysicalDimension.Height / page.Canvas.ClientSize.Height;  
float fitRate = Math.Max(widthFitRate, heightFitRate);  
float fitWidth = image.PhysicalDimension.Width / fitRate;  
float fitHeight = image.PhysicalDimension.Height / fitRate;  
//Draw image on page
page.Canvas.DrawImage(image, 30, 30, fitWidth, fitHeight);  
//Save the file
doc.SaveToFile("image to pdf.pdf");
doc.Close();