First, I’ll post the code I wrote, and then explain the issues at the end:
/// <summary>
/// 为pdf添加水印
/// </summary>
/// <param name="DocuementFileName">文档名称</param>
/// <param name="Save…...transparency doesn’t seem to take effect—even when set to 0.5, it appears...transparency settings not taking effect for PDFs exported from CorelDRAW...