//create a new word document and add a section and paragraph to it.
Document doc = new Document();
Section sec = doc.AddSection();
Paragraph para = sec.AddParagraph();

//Add the text strings to the paragraph and set the style
para.AppendHTML("
Add a new paragraph to the word and set the spacing
");
para.ApplyStyle(BuiltinStyle.Heading1);

//set the spacing before and after
para.Format.BeforeAutoSpacing = false;
para.Format.BeforeSpacing = 20;
para.Format.AfterAutoSpacing = false;
para.Format.AfterSpacing = 20;

//save the document to file
doc.SaveToFile("Result1.docx");

using Spire.Doc;
using Spire.Doc.Documents;
using Spire.Doc.Fields;
namespace SetSpacing
{
 class Program
    {

     static void Main(string[] args)
     {
         //create a new word document and load the sample from file
         Document document = new Document();
         document.LoadFromFile("sample.docx", FileFormat.Docx);

         //Add the text strings to the paragraph and set the style
         Paragraph para = new Paragraph(document);
         TextRange textRange1 = para.AppendText("This is a inserted paragraph.");
         textRange1.CharacterFormat.TextColor = Color.Blue;
         textRange1.CharacterFormat.FontSize = 15;

         //set the spacing before and after
         para.Format.BeforeAutoSpacing = false;
         para.Format.BeforeSpacing = 10;
         para.Format.AfterAutoSpacing = false;
         para.Format.AfterSpacing = 10;

         //insert the added paragraph to the word document
         document.Sections[0].Paragraphs.Insert(1, para);

         //save the document to file
         document.SaveToFile("Result2.docx", FileFormat.Docx2010);
     }

    }
}