ASP.NET PDF Viewer Control
How to read, view Microsoft Excel with page size setting using C# in ASP.NET

    public byte[] ApplyAddonExcelInOpenFunction(String srcFilePath)
    {
        //  Load source .xlsx file.
        XLSXDocument doc = new XLSXDocument(srcFilePath);
        //  Convert to PDF file with one page for each sheet by actual size.
        using (MemoryStream ms = new MemoryStream())
        {
            doc.ConvertToDocument(DocumentType.PDF, ms);

            using (MemoryStream oStream = new MemoryStream())
            {
                //  Expected page size: width = 8.5 inches; height 11 inches.
                SizeF size = new SizeF(8.5F, 11F);
                //  Fill mode for the sheet content: Fit Width
                PageArrangeOptions.PageFitMode fillMode = PageArrangeOptions.PageFitMode.FitWidth;
                //  Change PDF pages to the specified size.
                PDFDocument.ChangePageSize(ms, oStream, size, fillMode);
                return oStream.ToArray();
            }
        }
    }

<%@ WebHandler Language="C#" Class="UserCommandProcessHandler" %>

using System;
using System.IO;
using System.Drawing;
using System.Web;
using RasterEdge.Imaging.Basic;
using RasterEdge.XDoc.PDF;
using RasterEdge.XDoc.Excel;
using RasterEdge.WDP;
using RasterEdge.XDoc.PDF.HTML5Editor;

public class UserCommandProcessHandler : ProcessHandler
{

    /*
         The SDK will use the following url parameter names, please do not use them
          RECommand, src, filepath, restful
    */
    public override PDFWebDocument FileProcess()
    {
        HttpRequest request = this.Context.Request;

        if (!String.IsNullOrEmpty(request.QueryString["yourtarget"]))
        {
            // load file
            String docid = request.QueryString["yourtarget"];
            try
            {
                if (String.IsNullOrEmpty(docid) || !docid.EndsWith(".xlsx"))
                    throw new Exception("Source file must be a .xlsx file.");

                byte[] dataBytes = ApplyAddonExcelInOpenFunction(@"C:\\temp\" + docid);
                String fileName = docid.Replace(".xlsx", ".pdf");
                return REProcessControl.PageLoadFile(request, this.Manager, dataBytes, fileName);
            }
            catch (Exception ex)
            {
                Logger.Log("FileProcess: fail to open file " + docid + ". " + ex.Message, LogType.ERROR);
                return null;
            }
        }
        else
        {
            Logger.Log(">>> Unknown load file mode. Load default file defined in Web.config.", LogType.DEBUG);

            // load default file. defined in Web.config
            return REProcessControl.PageLoadFile(request, this.Manager, "", LoadType.Server);
        }
    }

    //  fid: Task ID.
    //  savePath: The abosolute path of the saved PDF file in the task's output folder.
    //  responseMsg: The response message for saving the current document to the task's output folder.
    //               The string value is the relative path of the output file. "Error" means that the saving process is failed.
    public override void SaveFile_OnServer(String fid, String savePath, String responseMsg)
    {
        //  You can process saved pdf document here, like add watermark, ...
        var documentPath = savePath;
        if (!String.IsNullOrEmpty(documentPath))
        {
            Logger.LogFile(fid, "SaveFileOnServer: output file path " + documentPath, LogType.DEBUG);

            //  To verify the output file.
            RasterEdge.Imaging.Basic.BaseDocument document = null;
            if (documentPath.EndsWith(".pdf"))
            {
                // document object includes user modified content
                document = new RasterEdge.XDoc.PDF.PDFDocument(documentPath);
            }
            if (document != null)
            {
                RasterEdge.XDoc.PDF.PDFDocument pdfDoc = document as RasterEdge.XDoc.PDF.PDFDocument;
                try
                {
                    //  Post-process
                    RasterEdge.XDoc.PDF.PDFMetadata metadata = pdfDoc.GetDescription();
                    metadata.Producer = "RasterEdge EdgePDF";
                    pdfDoc.SetDescription(metadata);
                }
                catch (Exception ex)
                {
                    //  Process error code, and return error information here
                    Logger.LogFile(fid, ex.Message + ". fail to do post-process.", LogType.ERROR);
                }

                //  Get the upload information of the file
                RasterEdge.WDP.DocUploadInfo docinfo = RasterEdge.WDP.Manager.FileManager.getUploadinfoByFid(fid);
                //  Get your file open url parameters value, if needed.
                String paraFilepathValue = docinfo.GetRequestParameters("yourtarget");
                if (!String.IsNullOrEmpty(paraFilepathValue))
                {
                    try
                    {
                        //  Replace file extension (".xlsx") to ".pdf".
                        int index = paraFilepathValue.LastIndexOf('.');
                        if (index > 0)
                            paraFilepathValue = paraFilepathValue.Substring(0, index);
                        pdfDoc.Save(@"C:\temp\" + paraFilepathValue + ".pdf");
                    }
                    catch (Exception ex)
                    {
                        //  Process error code, and return error information here
                        Logger.LogFile(fid, ex.Message + ". fail to save file to server.", LogType.ERROR);
                    }
                }
                else
                {
                    Logger.LogFile(fid, "no 'yourtarget' in the HTTPRequest.", LogType.INFO);
                }
            }
            else
            {
                Logger.LogFile(fid, "output PDF file is invalid.", LogType.ERROR);
            }
        }
        else
        {
            Logger.LogFile(fid, "fail to save file to server. output file path is null or empty.", LogType.ERROR);
        }
    }

    public byte[] ApplyAddonExcelInOpenFunction(String srcFilePath)
    {
        //  Load source .xlsx file.
        XLSXDocument doc = new XLSXDocument(srcFilePath);
        //  Convert to PDF file with one page for each sheet by actual size.
        using (MemoryStream ms = new MemoryStream())
        {
            doc.ConvertToDocument(DocumentType.PDF, ms);

            using (MemoryStream oStream = new MemoryStream())
            {
                //  Expected page size: width = 8.5 inches; height 11 inches.
                SizeF size = new SizeF(8.5F, 11F);
                //  Fill mode for the sheet content: Fit Width
                PageArrangeOptions.PageFitMode fillMode = PageArrangeOptions.PageFitMode.FitWidth;
                //  Change PDF pages to the specified size.
                PDFDocument.ChangePageSize(ms, oStream, size, fillMode);
                return oStream.ToArray();
            }
        }
    }
}