Add support for the creation of AES-encrypted archives.

There is a related feature request for the extraction of such archives: ZipLibrary: Add support for extraction of AES-encrypted archives.

When exporting a document with the .NET Framework implementation, only subsets of the used fonts are embedded in the document. 

This is currently not available in the Silverlight implementation, and it most probably won't be available in the .NET Standard implementation, as the current implementation is dependent on the WPF font classes.

Provide API to plug similar logic when using different platforms as well.
This item wil handle the TrueType OpenType Font format. For the Compact Font Format (CFF) please follow: Export subset of Compact Font Format (CFF) fonts for platforms different than .NET Framework

ZUGFeRD (acronym for Zentraler User Guide des Forums elektronische Rechnung Deutschland) is a specification for the electronic invoice format of the same name.

The feature depends on the following features:

• Support for embedded file streams
• Support for metadata streams (XMP metadata)

Currently, a NullReferenceException is thrown because of the incorrect structure. 

As a workaround, the exception can be handled using the Handling Exceptions mechanism.

Update:
When importing documents with invalid structure of path construction operators an InvalidGraphicOperandsCountException is thrown which could be handled using the Handling Exceptions mechanism.

PdfFormatProvider provider = new PdfFormatProvider();
provider.ImportSettings.DocumentUnhandledException += this.ImportSettings_DocumentUnhandledException;

private void ImportSettings_DocumentUnhandledException(object sender, DocumentUnhandledExceptionEventArgs e)
{
    if (e.Exception is InvalidGraphicOperandsCountException)
    {
        e.Handled = true;
    }
}

According to the PDF specification:
A clipping path operator (W or W*) may appear after the last path construction operator and before the path-painting operator that terminates a path object.

Invalid:

W                          % clipping path operator
0 0 m                     % start of the path construction
596 0 l
596 842 l
0 842 l
h                            % end of the path construction
n                            % path-painting operator

0 0 m
596 0 l
596 842 l
0 842 l
h
W
n

Currently (in the invalid cases), the path construction is skipped on import.

Currently, when registering *.otf font file with FontsRepository.RegisterFont method an exception is thrown during the font creation. 

WORKAROUND:  The font file may be converted to TTF format (*.ttf) which is successfully registered. This conversion may be achieved with FontForge by opening the font file and then choosing File -> Generate Fonts -> TrueType -> Generate. More information on FontForge program may be found here: https://fontforge.github.io/en-US/

Handle import of documents with self-referring styles.

As a workaround, you can go through the RTF document structure of a single file and utilize Regex to resolve the self-referring styles like this:

string rtf = File.ReadAllText("inputFile.rtf");
rtf = FixSelfReferringStyles(rtf);

Telerik.Windows.Documents.Flow.FormatProviders.Rtf.RtfFormatProvider provider = new Telerik.Windows.Documents.Flow.FormatProviders.Rtf.RtfFormatProvider(); 

 var document = provider.Import(rtf);

...

private static string FixSelfReferringStyles(string rtf)
{
    string regexString = @"{\\s([0-9]+)[^}]*\\slink([0-9]+)";

    var matches = Regex.Matches(rtf, regexString);
    foreach (Match match in matches)
    {
        if (match.Groups[1].Value == match.Groups[2].Value)
        {
            var oldValue = match.Groups[0].Value;
            var newValue = oldValue.Replace(@" \slink" + match.Groups[1].Value, string.Empty);
            rtf = rtf.Replace(oldValue, newValue);
        }
    }

    return rtf;
}

Add support for extraction of AES-encrypted archives.

There is a related feature request for the creation of such archives: ZipLibrary: Add support for creation of AES-encrypted archives.

They are exported with the /EmbeddedFiles switch. This would allow adding external files to the PDF document.

Add support for shapes, and especially for shapes with textual content. 
In OOXML, shapes are represented by the wps:wsp element, and shapes with textual content by <wps:txbx>, <w:txbxContent>.
Such shape can be added to a Word document using the Insert -> Text -> Text Box -> Draw Text Box, or through a shape's context menu -> Add Text.

Do not confuse these shapes with Text/Rich Text content controls (see https://feedback.telerik.com/Project/184/Feedback/Details/190057 )