var rtf = File.ReadAllText(fileName);
rtf = this.RenameStyleDifferentInOnlySpaces(rtf);
var document = provider.Import(rtf);

...

private string RenameStyleDifferentInOnlySpaces(string rtf)
{
    HashSet<string> styles = new HashSet<string>();

    string pattern = @"{\\(?:\*\\c)?s([0-9]+)[^}]*\n?[^}]*\\[^' ]* ?'?([^;]*)";

    var matches = Regex.Matches(rtf, pattern);
    foreach (Match match in matches)
    {
        string styleName = match.Groups[2].Value.Replace(" ", string.Empty);
        if (styles.Contains(styleName))
        {
            styleName = this.ReplaceOldStyleName(ref rtf, styles, match).Replace(" ", string.Empty);
        }

        styles.Add(styleName);
    }

    return rtf;
}

private string ReplaceOldStyleName(ref string rtf, HashSet<string> styles, Match match)
{
    string oldStyleName = match.Groups[2].Value;
    StringBuilder styleNameBuilder = new StringBuilder(oldStyleName + "0");
    while (styles.Contains(styleNameBuilder.ToString().Replace(" ", string.Empty)))
    {
        styleNameBuilder.Append("0");
    }

    string oldMatch = match.Groups[0].Value;
    string newMatch = oldMatch.Replace(oldStyleName, styleNameBuilder.ToString());
    rtf = rtf.Replace(oldMatch, newMatch);
    return styleNameBuilder.ToString();
}

   at Telerik.Windows.Documents.Core.Fonts.Type1.Type1Format.Type1FontSource.GetFontFamily()

This exception was originally thrown at this call stack:
    Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.DocumentStructure.DocumentCatalog.CopyEmbeddedFilesTo(Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Import.Parser.PostScriptReader, Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Import.IRadFixedDocumentImportContext) in DocumentCatalog.cs

RtfFormatProvider provider = new RtfFormatProvider();
var rtf = File.ReadAllText(ofd.FileName);
rtf = this.ReplaceSelfBasedOnStyle(rtf);
this.flowDocument = provider.Import(rtf);

...

private string ReplaceSelfBasedOnStyle(string rtf)
{
    string pattern = @"{[\n]*\\s[0-9]+[^;]* \\\w* (Normal);}";

    var matches = Regex.Matches(rtf, pattern);
    foreach (Match match in matches)
    {
        string oldValue = match.Value;
        string newValue = oldValue.Replace(@"\sbasedon0 ", string.Empty);

        rtf = rtf.Replace(oldValue, newValue);
    }

    return rtf;
}

    Sub Main()
        Dim sZipFilePath As String = "..\..\test.zip"
        File.Delete(sZipFilePath)

        CreateArchive(sZipFilePath)

        Dim decryptionSettings As DecryptionSettings = EncryptionSettings.CreateDecryptionSettings()
        AddHandler decryptionSettings.PasswordRequired, AddressOf DecryptionSettings_PasswordRequired
        Dim compressionSettings As CompressionSettings = Nothing
        Dim encoding As Encoding = Nothing
        Using oFS As FileStream = File.Open(sZipFilePath, FileMode.OpenOrCreate)


            Using oArchive As ZipArchive = ZipArchive.Update(oFS, encoding, compressionSettings, decryptionSettings)
                For Each entry As ZipArchiveEntry In oArchive.Entries
                    Using entryStream As Stream = entry.Open()
                        Dim reader As New StreamReader(entryStream)
                        Dim content As String = reader.ReadToEnd()

                        entryStream.Seek(0, SeekOrigin.End)
                        Dim writer As New StreamWriter(entryStream)
                        writer.WriteLine("Updated line.")
                        writer.Flush()
                    End Using
                Next
            End Using
        End Using
    End Sub

    Private Sub CreateArchive(sZipFilePath As String)
        Using stream As Stream = File.Open(sZipFilePath, FileMode.Create)
            Dim encryptionSettings As PasswordEncryptionSettings = encryptionSettings.CreatePkzipPasswordEncryptionSettings()
            encryptionSettings.Password = "MyPassword"
            Dim compressionSettings As CompressionSettings = Nothing
            Dim encoding As Encoding = Nothing

            Using archive As ZipArchive = ZipArchive.Create(stream, encoding, compressionSettings, encryptionSettings)

                Using entry As ZipArchiveEntry = archive.CreateEntry("text.txt")
                    Dim writer As StreamWriter = New StreamWriter(entry.Open())
                    writer.WriteLine("Hello world!")
                    writer.Flush()
                End Using
            End Using
        End Using
    End Sub

    Private Sub DecryptionSettings_PasswordRequired(ByVal sender As Object, ByVal e As PasswordRequiredEventArgs)
        e.Password = "MyPassword"
    End Sub

        static void Main(string[] args)
        {
            string archiveFileName = @"..\..\myzip.zip";
            string sourceDirectoryName = @"..\..\Folder";
            File.Delete(archiveFileName);
            Telerik.Windows.Zip.Extensions.ZipFile.CreateFromDirectory(sourceDirectoryName, archiveFileName, Telerik.Windows.Zip.CompressionLevel.Optimal, true);

            using (Stream stream = File.Open(archiveFileName, FileMode.Open))
            {

            }
        }

        static void Main(string[] args)
        {
            string archiveFileName = @"..\..\myzip.zip";
            string sourceDirectoryName = @"..\..\Folder";
            File.Delete(archiveFileName);

          //  Telerik.Windows.Zip.Extensions.ZipFile.CreateFromDirectory(sourceDirectoryName, archiveFileName, Telerik.Windows.Zip.CompressionLevel.Optimal, true);
            CreateFromDirectory(sourceDirectoryName, archiveFileName, Telerik.Windows.Zip.CompressionLevel.Optimal, true);

            using (Stream stream = File.Open(archiveFileName, FileMode.Open))
            {

            }
        }

        private static void CreateFromDirectory(string sourceDirectoryName, string destinationArchiveFileName, Telerik.Windows.Zip.CompressionLevel compressionLevel, bool includeBaseDirectory)
        {
            Encoding entryNameEncoding = null;
            DeflateSettings compressionSettings = new DeflateSettings()
            {
                CompressionLevel = compressionLevel,
                HeaderType = CompressedStreamHeader.None
            };
            char[] directorySeparatorChar = new char[] { Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar };

            sourceDirectoryName = Path.GetFullPath(sourceDirectoryName);
            destinationArchiveFileName = Path.GetFullPath(destinationArchiveFileName);
            FileStream fileStream = File.Open(destinationArchiveFileName, FileMode.CreateNew, FileAccess.Write, FileShare.None); ;
            using (ZipArchive zipArchive = new ZipArchive(fileStream, ZipArchiveMode.Create,false,  entryNameEncoding))
            {
                bool empty = true;

                DirectoryInfo directoryInfo = new DirectoryInfo(sourceDirectoryName);
                string fullName = directoryInfo.FullName;
                if (includeBaseDirectory && directoryInfo.Parent != null)
                {
                    fullName = directoryInfo.Parent.FullName;
                }

                foreach (FileSystemInfo fileSystemInfo in directoryInfo.EnumerateFileSystemInfos("*", SearchOption.AllDirectories))
                {
                    empty = false;

                    int length = fileSystemInfo.FullName.Length - fullName.Length;
                    string entryName = fileSystemInfo.FullName.Substring(fullName.Length, length);
                    entryName = entryName.TrimStart(directorySeparatorChar);

                    DirectoryInfo subfolder = fileSystemInfo as DirectoryInfo;
                    if (subfolder != null)
                    {
                        if (IsDirectoryEmpty(subfolder))
                        {
                            zipArchive.CreateEntry(string.Concat(entryName, Path.DirectorySeparatorChar));
                        }
                    }
                    else
                    {
                        ZipFile.CreateEntryFromFile(zipArchive, fileSystemInfo.FullName, entryName, compressionSettings);
                    }
                }

                if (includeBaseDirectory && empty)
                {
                    zipArchive.CreateEntry(string.Concat(directoryInfo.Name, Path.DirectorySeparatorChar));
                }
            }
        }
        private static bool IsDirectoryEmpty(DirectoryInfo directoryInfo)
        {
            bool empty = true;

            using (IEnumerator<FileSystemInfo> enumerator = directoryInfo.EnumerateFileSystemInfos("*", SearchOption.AllDirectories).GetEnumerator())
            {
                if (enumerator.MoveNext())
                {
                    empty = false;
                }
            }

            return empty;
        }