private  void MergeDifferentDocumentsPagesWithFixed()
        {
            string[] documentsToMerge =
            {
                "14301-STOCK_Proforma.pdf",
                "14302-STOCK_Proforma.pdf",
                "14303-STOCK_Proforma.pdf",
                "14304-STOCK_Proforma.pdf",
                "14305-STOCK_Proforma.pdf",
                "14330-STOCK_Proforma.pdf"
            };
            RadFixedDocument doc = new RadFixedDocument();
            PdfFormatProvider provider = new PdfFormatProvider();
            foreach (string current_item in documentsToMerge)
            {
                string path = @"..\..\Samples\" + current_item;
                RadFixedDocument docToMerge;
                if (!File.Exists(path))
                {
                    continue;
                }
                using (Stream stream = File.OpenRead(path))
                {
                    docToMerge = provider.Import(stream);
                }
                doc.Merge(docToMerge);
            }


            string outputFilePath = @"..\..\mergedFixed.pdf";
            File.Delete(outputFilePath);

            using (Stream output = File.OpenWrite(outputFilePath))
            {
                provider.Export(doc, output);
            }
            Process.Start(new ProcessStartInfo() { FileName = outputFilePath, UseShellExecute = true });


        }

   private void MergeDifferentDocumentsPages(string resultFileName)
   {
       string[] documentsToMerge =
       {
           "14301-STOCK_Proforma.pdf",
           "14302-STOCK_Proforma.pdf",
           "14303-STOCK_Proforma.pdf",
           "14304-STOCK_Proforma.pdf",
           "14305-STOCK_Proforma.pdf",
           "14330-STOCK_Proforma.pdf"
       };

       File.Delete(resultFileName);
       using (PdfStreamWriter fileWriter = new PdfStreamWriter(File.OpenWrite(resultFileName)))
       {
           foreach (string documentName in documentsToMerge)
           {
               string path = @"..\..\Samples\" + documentName;
               using (PdfFileSource fileToMerge = new PdfFileSource(File.OpenRead(path)))
               {
                   foreach (PdfPageSource pageToMerge in fileToMerge.Pages)
                   {
                       fileWriter.WritePage(pageToMerge);
                   }
               }
           }
       }


      
       Process.Start(new ProcessStartInfo() { FileName = resultFileName, UseShellExecute = true });
   }

	<sheetData>
		<row r="1" spans="1:2" x14ac:dyDescent="0.35">
			<c r="A1"><v>1</v></c>
			<c r="B1"><v>2</v></c>
		</row>
		<row r="2" spans="1:2" s="1" customFormat="1" x14ac:dyDescent="0.35"/>
	</sheetData>

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)
			Using entry As ZipArchiveEntry = oArchive.CreateEntry("newText.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 CreateArchive(sZipFilePath As String)
	Using stream As Stream = File.Open(sZipFilePath, FileMode.Create)
		Dim _encryptionSettings As PasswordEncryptionSettings = EncryptionSettings.CreatePkzipPasswordEncryptionSettings()
		_encryptionSettings.Password = "telerik"
		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 = "telerik"
End Sub

ZipArchive archive = new ZipArchive(stream, ZipArchiveMode.Create, true, encoding, compressionSettings, encryptionSettings)

ZipArchive oArchive = new ZipArchive(stream, ZipArchiveMode.Update, true, encoding, compressionSettings, decryptionSettings)

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