In the current implementation, the parent of a hyperlink must be a paragraph. Otherwise, a NullReferenceException is thrown.

This element serves as a frame and allows the element to be positioned as a floating element. More information about it is available in section 22.9.2.18 ST_XAlign (Horizontal Alignment Location) of Open Office XML.
DECLINED: Duplicate with - Implement support for Text Frame Properties.

When importing documents containing pictures with references represented with the r:link attribute, ArgumentNullException is thrown.

Implement support for pictures with references represented with the r:link attribute in the schema.

Enable the customers to import SVG images and use them in their documents.

Implement support for footers in HtmlFormatProvider.

Enable the customers to add digital signatures to the documents and read signed documents.

When a document containing a field without a separator is inserted using the RadFlowDocumentEditor.InsertDocument(*) method, NullRferenceException is thrown.

Workaround: Fix the document before inserting: 

private static void WorkaroundFieldsIssue(RadFlowDocument flowdocument)
{
    foreach (FieldCharacter fieldCharacter in flowdocument.EnumerateChildrenOfType<FieldCharacter>().ToList())
    {
        // only for start
        if (fieldCharacter.FieldCharacterType == FieldCharacterType.Start)
        {
            if (fieldCharacter.FieldInfo.Separator != null && fieldCharacter.FieldInfo.Separator.Parent == null)
            {
                Paragraph parent = fieldCharacter.FieldInfo.End.Paragraph;
                int index = parent.Inlines.IndexOf(fieldCharacter.FieldInfo.End);

                fieldCharacter.FieldInfo.End.Paragraph.Inlines.Insert(index, fieldCharacter.FieldInfo.Separator);
            }
        }
    }
}

LineInfo objects are not cleared when there are tables in the document being exported to PDF which leads to OutOfMemoryException.

When the table borders are None, and each cell has custom set borders, when cells are merged, only borders of the cell that has <w:vMerge w:val="restart"/> are imported.

When the document contains an image with extension, which is not among the supported ones, a KeyNotFoundException is thrown during Import.

When exporting a nested table, which is inside a table with cells whose sum of widths is more than 100%, the last cells are missing from the exported with PdfFormatProvider document.

The issue is not observable in the other format providers.

Add support for importing HTML with syntax <img style="width: 300px; height: 300px;" /> At the moment only HTML attributes are supported.

Currently, the align attribute is supported only for a table and when applied to a cell or row is omitted on import.

There are multiple tags and attributes in the Open XML model which define the formatting of the complex script characters and are not implemented in the WordsProcessing model. 

Such tags are:
szCs: Complex script font size;
bCs: Complex script bold;
iCs: Complex script italic;

Attributes:
cstheme: Complex Script Theme Font;

The cs (Complex Script Font) attribute is implemented in the export, but it is not preserved in the model on import.

When text content (text in paragraph, text in span) in HTML contains line break (\r, \n, or \r\n), it should be imported as space. Instead, the new lines are currently removed. 

For example, <p>first\nsecond</p> (line feed between the words) is imported as run with content "firstsecond" instead of "first second".

Applying border="1" to a table element, should set table cells borders to the same value. Currently, only the table borders are set.

When the RowSpan value is bigger than the available rows, a ArgumentOutOfRangeException is thrown while exporting the document.

Workaround: Change the value of RowSpan after importing:

foreach (var cell in document.EnumerateChildrenOfType<TableCell>())
{
    while (cell.RowSpan > cell.Row.Table.Rows.Count)
    {
        cell.RowSpan--;
    }
}

When a table cell has a smaller width set and inside there is a paragraph with larger indent set or bullets, the table does not expand in order to show the text and the text becomes invisible.

Applying LockAspectRatio to an image is not respected after opening the document in MS Word - the LockAspectRatio checkbox in the is not checked. An additional XML element (cNvGraphicFramePr) should be added so the UI can respect it.