PdfSharp. dll changes the pdf settings. For example, if you cannot renew or print the settings

And reference PdfSharp. dll

 

Using sharp. Pdf;

Using System. IO;

 

 public string PDFSecurity(string strSourcePDFFile, string strDestPDFFile, bool AddUserPassword, string strPassword)        {            try            {                PdfSharp.Pdf.PdfDocument pdfsourcedoc = PdfSharp.Pdf.IO.PdfReader.Open(strSourcePDFFile, PdfSharp.Pdf.IO.PdfDocumentOpenMode.Modify);                pdfsourcedoc.SecuritySettings.DocumentSecurityLevel = PdfSharp.Pdf.Security.PdfDocumentSecurityLevel.Encrypted128Bit;                pdfsourcedoc.SecuritySettings.OwnerPassword = "adamtest";                pdfsourcedoc.SecuritySettings.PermitAccessibilityExtractContent = false;                pdfsourcedoc.SecuritySettings.PermitAnnotations = false;                pdfsourcedoc.SecuritySettings.PermitAssembleDocument = false;                pdfsourcedoc.SecuritySettings.PermitExtractContent = false;                pdfsourcedoc.SecuritySettings.PermitFormsFill = false;                pdfsourcedoc.SecuritySettings.PermitFullQualityPrint = false;                pdfsourcedoc.SecuritySettings.PermitModifyDocument = false;                pdfsourcedoc.SecuritySettings.PermitPrint = false;                if (AddUserPassword == true)                {                    pdfsourcedoc.SecuritySettings.UserPassword = strPassword;                }                pdfsourcedoc.Save(strDestPDFFile);                return "";            }            catch (Exception ex)            {                return ex.ToString();            }                }