Download HTML Content as PDF

1. Download and install wkhtmltopdf.
2. Use the below code.

public static string HtmlToPdf(string outputFilenamePrefix, string[] urls,
    string[] options = null,
    string pdfHtmlToPdfExePath = @"C:\Program Files\wkhtmltopdf\bin\wkhtmltopdf.exe")
{
    string urlsSeparatedBySpaces = string.Empty;
    try
    {
        //Determine inputs
        if ((urls == null) || (urls.Length == 0))
            throw new Exception("No input URLs provided for HtmlToPdf");
        else
            urlsSeparatedBySpaces = String.Join(" ", urls); //Concatenate URLs

        string outputFilename = outputFilenamePrefix + "_" + DateTime.Now.ToString("yyyy-MM-dd-hh-mm-ss-fff") + ".PDF"; // assemble destination PDF file name

        var p = new System.Diagnostics.Process()
        {
            StartInfo =
            {
                FileName = pdfHtmlToPdfExePath,
                Arguments = ((options == null) ? "" : string.Join(" ", options)) + " " + urlsSeparatedBySpaces + " " + outputFilename,
                UseShellExecute = false, // needs to be false in order to redirect output
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                RedirectStandardInput = true, // redirect all 3, as it should be all 3 or none
                WorkingDirectory = Path.Combine(Path.GetDirectoryName(Assembly.GetEntryAssembly().Location))
            }
        };

        p.Start();

        // read the output here...
        var output = p.StandardOutput.ReadToEnd();
        var errorOutput = p.StandardError.ReadToEnd();

        // ...then wait n milliseconds for exit (as after exit, it can't read the output)
        p.WaitForExit(60000);

        // read the exit code, close process
        int returnCode = p.ExitCode;
        p.Close();

        // if 0 or 2, it worked so return path of pdf
        if ((returnCode == 0) || (returnCode == 2))
            return outputFilename;
        else
            throw new Exception(errorOutput);
    }
    catch (Exception exc)
    {
        throw new Exception("Problem generating PDF from HTML, URLs: " + urlsSeparatedBySpaces + ", outputFilename: " + outputFilenamePrefix, exc);
    }
}

1. And call the above method as HtmlToPdf("test", new string[] { "https://www.google.com" }, new string[] { "-s A5" });
2. If you need to convert HTML string to PDF, the tweak the above method and replace the Arguments to Process StartInfo as $@"/C echo | set /p=""{htmlText}"" | ""{pdfHtmlToPdfExePath}"" {((options == null) ? "" : string.Join(" ", options))} - ""C:\Users\xxxx\Desktop\{outputFilename}""";

You can take the HTML page and convert it to PDF through a backend service using the DocumentConverter. Here is an example you can leverage: 

using (DocumentConverter documentConverter = new DocumentConverter())         
{         
   var input = @"C:\Inputfiles\page.html");        
   var output = @"C:\Outputfiles\output.pdf");         
   var jobData = DocumentConverterJobs.CreateJobData(input, output, DocumentFormat.Pdf);         
   jobData.JobName = "Convert 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-core-convert-files-with-the-document-converter.html
https://www.leadtools.com/help/sdk/tutorials/dotnet-core-configure-and-run-the-document-service.html

1. using System.IO;  
2. using iTextSharp.text;  
3. using iTextSharp.text.pdf;  
4. using iTextSharp.text.html;  
5. using iTextSharp.text.html.simpleparser;  
6. using iTextSharp.tool.xml;  
7.   
8.   //-(Get it here)-- https://sourceforge.net/projects/itextsharp/
9.   
10. byte[] pdf; // result will be here  
11. var cssText = File.ReadAllText(HttpContext.Current.Server.MapPath("~/css/test.css"));  
12. var html = File.ReadAllText(HttpContext.Current.Server.MapPath("~/css/test.html"));  
13.   
14.             using (var memoryStream = new MemoryStream())  
15.             {  
16.                 var document = new iTextSharp.text.Document(iTextSharp.text.PageSize.A4, 50, 50, 60, 60);  
17.                 var writer = PdfWriter.GetInstance(document, memoryStream);  
18.                 document.Open();  
19.                 using (var cssMemoryStream = new MemoryStream(System.Text.Encoding.UTF8.GetBytes(cssText)))  
20.                 {  
21.                     using (var htmlMemoryStream = new MemoryStream(System.Text.Encoding.UTF8.GetBytes(html)))  
22.                     {  
23.                         XMLWorkerHelper.GetInstance().ParseXHtml(writer, document, htmlMemoryStream, cssMemoryStream);  
24.                     }  
25.                 }  
26.                 document.Close();  
27.                 pdf = memoryStream.ToArray();  
28.                 //pOutputPDFilename  
29.                 File.WriteAllBytes(pOutputPDFilename, pdf);  
30.             }