1、WPS安装，最好用这个版本别的版本不清楚，安装Pro Plus2016版本。

https://ep.wps.cn/product/wps-office-download.html

2、添加相关的引用：wpsapiex.dll,etapi.dll,wppapi.dll,wpsapi.dll，目前就发现这几个

3、代码类如下

/// <summary>  
/// WPS文件转Pdf类  
/// </summary>  
public class ToPdfHelper : IDisposable  
{  
    /// <summary>  
    /// 是否杀死全部WPS程序  
    /// </summary>  
    public bool IsKillAllWps = false;  
    //Wps的动态对象  
    dynamic wps;  
    /// <summary>  
    /// 初始化类基础信息  
    /// </summary>  
    /// <param name="FilePath">文件路径</param>  
    /// <param name="IsKillAllWps">转换完成后是否杀死全部WPS应用</param>  
    public ToPdfHelper(string FilePath, bool IsKillAllWps = false)  
    {  
        if (File.Exists(FilePath))  
        {  
            this.IsKillAllWps = IsKillAllWps;  
            this.FilePath = FilePath;  
            string Extension = Path.GetExtension(FilePath).ToLower();//扩展名 ".aspx"  
            switch (Extension)  
            {  
                case "xls":  
                    Extension = "KET.Application";  
                    break;  
                case "xlsx":  
                    Extension = "KET.Application";  
                    break;  
                case "ppt":  
                    Extension = "KWPP.Application";  
                    break;  
                case "pptx":  
                    Extension = "KWPP.Application";  
                    break;  
                default:  
                    Extension = "KWps.Application";  
                    break;  
            }  
            Type type = Type.GetTypeFromProgID(Extension);  
            if (type == null)  
            {  
                Extension = "wps.Application";  
                type = Type.GetTypeFromProgID("wps.Application");  
            }  
            wps = Activator.CreateInstance(type);  
            //比较完整的一些  
            //WPS文字           KWPS.Aplication  
            //WPS的Excel        KET.Application  
            //WPS的演示文档     KWPP.Application  
            //Word              Word.Application  
            //Excel             Excel.Application  
            //Powerpoint        Powerpoint.Application  
        }  
        else  
        {  
            throw new Exception("找不到原文件，请检查！");  
        }  
    }  
    /// <summary>  
    /// 源文件路径  
    /// </summary>  
    public string FilePath { get; set; }  
    /// <summary>  
    /// 使用wps将Word转PDF  
    /// </summary>  
    /// <param name="TargetPath">目标文件路径，不传默认在源文件的所属目录</param>  
    /// <returns>Pdf文件路径</returns>  
    public string WordWpsToPdf(string TargetPath = "")  
    {  
        if (string.IsNullOrEmpty(FilePath))  
        {  
            throw new Exception("请传入文件路径");  
        }  
        //如果没传入文件路径就默认使用源目录  
        if (string.IsNullOrEmpty(TargetPath))  
        {  
            TargetPath = Path.ChangeExtension(FilePath, "pdf");  
        }  
        try  
        {  
            //忽略警告提示  
            wps.DisplayAlerts = false;  
            //用wps 打开word不显示界面  
            dynamic doc = wps.Documents.Open(FilePath, Visible: false);  
            //保存为Pdf  
            doc.ExportAsFixedFormat(TargetPath, Word.WdExportFormat.wdExportFormatPDF);  
            //设置隐藏菜单栏和工具栏  
            //wps.setViewerPreferences(PdfWriter.HideMenubar | PdfWriter.HideToolbar);  
            doc.Close();  
            doc = null;  
        }  
        catch (Exception e)  
        {  
            throw e;  
        }  
        finally  
        {  
            Dispose();  
        }  
        return TargetPath;  
    }  
    /// <summary>  
    /// 使用wps将xls转PDF  
    /// </summary>  
    /// <param name="TargetPath">目标文件路径，不传默认在源文件的所属目录</param>  
    /// <returns>Pdf文件路径</returns>  
    public string XlsWpsToPdf(string TargetPath = "")  
    {  
        if (string.IsNullOrEmpty(FilePath))  
        {  
            throw new Exception("请传入文件路径");  
        }  
        //如果没传入文件路径就默认使用源目录  
        if (string.IsNullOrEmpty(TargetPath))  
        {  
            TargetPath = Path.ChangeExtension(FilePath, "pdf");  
        }  
        try  
        {  
            XlFixedFormatType targetType = XlFixedFormatType.xlTypePDF;  
            object missing = Type.Missing;  
            //忽略警告提示  
            wps.DisplayAlerts = false;  
            //xls 转pdf  
            dynamic doc = wps.Application.Workbooks.Open(FilePath, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing);  
            //保存为Pdf  
            doc.ExportAsFixedFormat(targetType, TargetPath, XlFixedFormatQuality.xlQualityStandard, true, false, missing, missing, missing, missing);  
            //设置隐藏菜单栏和工具栏  
            //wps.setViewerPreferences(PdfWriter.HideMenubar | PdfWriter.HideToolbar);  
            doc.Close();  
            doc = null;  
        }  
        catch (Exception e)  
        {  
            throw e;  
        }  
        finally  
        {  
            Dispose();  
        }  
        return TargetPath;  
    }

    /// <summary>  
    /// 使用ppt将xls转PDF  
    /// </summary>  
    /// <param name="TargetPath">目标文件路径，不传默认在源文件的所属目录</param>  
    /// <returns>Pdf文件路径</returns>  
    public string PptWpsToPdf(string TargetPath = "")  
    {  
        if (string.IsNullOrEmpty(FilePath))  
        {  
            throw new Exception("请传入文件路径");  
        }  
        //如果没传入文件路径就默认使用源目录  
        if (string.IsNullOrEmpty(TargetPath))  
        {  
            TargetPath = Path.ChangeExtension(FilePath, "pdf");  
        }  
        try  
        {  
            //忽略警告提示  
            wps.DisplayAlerts = false;  
            //ppt 转pdf  
            dynamic doc = wps.Presentations.Open(FilePath, MsoTriState.msoCTrue,  
                MsoTriState.msoCTrue, MsoTriState.msoCTrue);  
            object missing = Type.Missing;  
            //doc.ExportAsFixedFormat(pdfPath, PpFixedFormatType.ppFixedFormatTypePDF,  
            //    PpFixedFormatIntent.ppFixedFormatIntentPrint,  
            //    MsoTriState.msoCTrue, PpPrintHandoutOrder.ppPrintHandoutHorizontalFirst,  
            //    PpPrintOutputType.ppPrintOutputBuildSlides,  
            //      MsoTriState.msoCTrue, null, PpPrintRangeType.ppPrintAll,"",  
            //      false, false, false, false, false, missing);  
            //保存为Pdf  
            doc.SaveAs(TargetPath, PowerPoint.PpSaveAsFileType.ppSaveAsPDF, MsoTriState.msoTrue);  
            //设置隐藏菜单栏和工具栏  
            //wps.setViewerPreferences(PdfWriter.HideMenubar | PdfWriter.HideToolbar);  
            doc.Close();  
            doc = null;  
        }  
        catch (Exception e)  
        {  
            throw e;  
        }  
        finally  
        {  
            Dispose();  
        }  
        return TargetPath;  
    }

    /// <summary>  
    /// 支持释放资源可以使用using  
    /// </summary>  
    public void Dispose()  
    {  
        if (wps != null)  
        {  
            wps.Quit();  
            //释放掉wps对象  
            wps = null;  
            #region 强制关闭所有wps的功能慎用,尤其是带并发的  
            //强制关闭所有wps进程,解决文件占用的问题  
            if (this.IsKillAllWps)  
            {  
                System.Diagnostics.Process\[\] process = System.Diagnostics.Process.GetProcessesByName("wps");  
                foreach (System.Diagnostics.Process prtemp in process)  
                {  
                    prtemp.Kill();  
                }  
            }  
            #endregion  
        }  
    }  
}

3、调用代码如下

    /// <summary>  
    /// 开始转换Pdf  
    /// </summary>  
    private void StatButton\_Click(object sender, EventArgs e)  
    {  
        if (File.Exists(PdfFileTextBox.Text)&& Path.IsPathRooted(PdfFileTextBox.Text))  
        {  
            Stopwatch sw = new Stopwatch();  
            sw.Start();  
            using (ToPdfHelper Help = new ToPdfHelper(PdfFileTextBox.Text,true))  
            {  
                Help.WordWpsToPdf();  
            }  
            sw.Stop();  
            TimeSpan ts2 = sw.Elapsed;  
            TimeLabel.Text = string.Format("转换使用时间：总共花费{0}ms.", ts2.TotalMilliseconds);  
        }  
        else  
        {  
            MessageBox.Show("文件不存在，检查文件路径是否正常，只支持绝对路径！");  
        }  
    }