According to the Pdf Specification: A given object number must not have an entry in more than one subsection within a single section.

The object on line 7 has object number 2, the same as of object on line 5.

Introduce an option to replace a Run text with line breaks and/or new lines or with other document elements such as Table, Image, Paragraph and etc. 

The following code snippet shows how a Run can be replaced with another inline element:

RadFlowDocument document = new RadFlowDocument();
RadFlowDocumentEditor editor = new RadFlowDocumentEditor(document);
 
editor.InsertText("text");
editor.InsertText("REMOVE");
editor.InsertText("text");
 
foreach (Run run in document.EnumerateChildrenOfType<Run>().ToList())
{
    if (run.Text == "REMOVE")
    {
        Paragraph paragraph = run.Paragraph;
        int childIndex = paragraph.Inlines.IndexOf(run);
 
        ImageInline image = new ImageInline(document);
        using (Stream stream = File.OpenRead("example_image.png"))
        {
            image.Image.ImageSource = new Telerik.Windows.Documents.Media.ImageSource(stream, "png");
        }
 
        paragraph.Inlines.Insert(childIndex, image);
        paragraph.Inlines.Remove(run);
    }
}

When a csv is exported the entire range which has values is exported. When export is done in Excel, the cells of this range which are empty are marked by an additional field, separated by a comma. This comma is present in SpreadProcessing only in places where it is obligatory for example in the middle of the row. Obligatory comma in this context means that without it the file will not be read correctly by Excel or SpreadProcessing. In places where it is not obligatory, like in an empty row or in the end of the row, it is skipped. These non-obligatory commas do not influence how the file will be interpreted by Excel, however, according to the most-popular csv spec, they should be present, which means that there could be parsers which are unable to parse the resulting file. (2.4 Each line should contain the same number of fields throughout the file.) 

Example:
Exported by Excel:
---------------------------------------
Product,Unit Price,Units in Stock,Discontinued
Chai,$18.00 ,39,
Chang,,17,
Chef Anton's Cajun Seasoning,$22.00 ,53,No
,,,
Chef Anton's Gumbo Mix,$21.35 ,0,No
---------------------------------------
Exported by SpreadProcessing:
---------------------------------------
Product,Unit Price,Units in Stock,Discontinued
Chai,$18.00 ,39
Chang,,17
Chef Anton's Cajun Seasoning,$22.00 ,53,No

Chef Anton's Gumbo Mix,$21.35 ,0,No
---------------------------------------
Note the extra commas in the empty row and in the end of the first two rows in the SpreadProcessing sample.

According to the OOXML specification the shading color can be defined only in RRGGBB hex color, but MS Word also supports colors defined with their names - e.g. "Red".

Enable the customers to work with .dot files.

Enable the customers to work with .doc files.

The API should allow you to perform a text-based search and return the parent element(s) of the result(s) or directly the found element(s).

 Exception trying to import HTML that contains width with an empty value. For example:

<table width="">

Add support for preserving and exporting the macros in a macro-enabled workbook.

Macros are pieces of code written in Visual Basic for Applications (VBA) which are used to automate repetitive tasks in excel. The macros are part of the excel file. When a file contains a macro its extension becomes xlsm.

SpreadProcessing should be able to import and export xlsm files and edit the macros in them.