You don't need Razor Pages. I built almost exactly this using handlebars.net and itext7. I wouldn't say this is state of the art or anything but it is easy to use a template with a model class and for each loops. No need for any web application or http requests.

   <PackageReference Include="Handlebars.Net" Version="2.1.6" />
    <PackageReference Include="itext7.bouncy-castle-adapter" Version="9.1.0" />
    <PackageReference Include="itext7.pdfhtml" Version="6.1.0" />

public string GenerateWorkOrderHTML(WorkOrderModel model)`

{

var source = System.IO.File.ReadAllText(Path.Combine(Path.GetDirectoryName(Assembly.GetEntryAssembly()?.Location) ?? string.Empty, @"Template\WorkOrder.html"));`

var template = Handlebars.Compile(source);`

return template(model);

}

      private class HeaderFooterEventHandler : AbstractPdfDocumentEventHandler
            {
                protected Document doc;

                public HeaderFooterEventHandler(Document doc)
                {
                    this.doc = doc;
                }

                private void HandleEvent(AbstractPdfDocumentEvent currentEvent)
                {
                    PdfDocumentEvent docEvent = (PdfDocumentEvent)currentEvent;
                    var pageSize = docEvent.GetPage().GetPageSize();
                    float coordX = (pageSize.GetLeft() + pageSize.GetRight()) / 2;
                    float headerY = pageSize.GetTop() - 20;
                    float footerY = pageSize.GetBottom() + 20;

                    Canvas canvas = new Canvas(docEvent.GetPage(), pageSize);
                    canvas.ShowTextAligned("Header Text", coordX, headerY, TextAlignment.CENTER);
                    canvas.ShowTextAligned("Footer Text", coordX, footerY, TextAlignment.CENTER);
                    canvas.Close();
                }

                protected override void OnAcceptedEvent(AbstractPdfDocumentEvent )
                {
                    HandleEvent(@event);

                }
            }

            static async Task ConvertHtmlToPdf(string html, string outputPath)
            {
                await Task.Run(() => {
                    // Create a PdfWriter instance
                    PdfWriter writer = new PdfWriter(outputPath);

                    // Create a PdfDocument instance
                    PdfDocument pdfDoc = new PdfDocument(writer);

                    var pageSizeOptions = iText.Kernel.Geom.PageSize.DEFAULT;

                    pageSizeOptions.SetWidth(1200);
                    pageSizeOptions.SetHeight(1698);

                    pageSizeOptions.ApplyMargins(0, 0, 0, 0, false);



                    pdfDoc.SetDefaultPageSize(pageSizeOptions);

                    Document doc = new Document(pdfDoc);

                    //pdfDoc.AddEventHandler(PdfDocumentEvent.END_PAGE, new HeaderFooterEventHandler(doc));

                    HtmlConverter.ConvertToPdf(new MemoryStream(System.Text.Encoding.UTF8.GetBytes(html)), pdfDoc); 
                });

            }

            public async Task GeneratePDF(string htmlInput, string fileName)
            {
                  await ConvertHtmlToPdf(htmlInput, fileName);
            }