Document document = new Document();
document.LoadFromFile(@"C:\Users\Administrator\Desktop\向日葵.docx", FileFormat.Docx);

Paragraph paraInserted = document.Sections[0].AddParagraph();
TextRange textRange1 = paraInserted.AppendText("向日葵的花语是——太阳、光辉、高傲、忠诚、爱慕、沉默的爱。向日葵又叫望日莲，一个很美的名字");
textRange1.CharacterFormat.TextColor = Color.Blue;
textRange1.CharacterFormat.FontSize = 15;
textRange1.CharacterFormat.UnderlineStyle = UnderlineStyle.Dash;

document.SaveToFile("result.docx", FileFormat.Docx);

Document doc = new Document();
doc.LoadFromFile(@"C:\Users\Administrator\Desktop\雏菊.docx", FileFormat.Docx);

Section sec = doc.Sections[0];
Paragraph para = sec.Paragraphs[sec.Paragraphs.Count - 1];

for (int i = 0; i < para.ChildObjects.Count;i++)
  {
  (para.ChildObjects[i] as TextRange).CharacterFormat.Hidden = true;

  }

doc.SaveToFile("result1.docx", FileFormat.Docx);

using Spire.Doc;
using Spire.Doc.Documents;
using Spire.Doc.Fields;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;

namespace insert_new_paragraph_and_hide
{
 class Program
 {
 static void Main(string[] args)
 { //该部分为插入新段落的代码
  Document document = new Document();
  document.LoadFromFile(@"C:\Users\Administrator\Desktop\向日葵.docx", FileFormat.Docx);

  Paragraph paraInserted = document.Sections[0].AddParagraph();
  TextRange textRange1 = paraInserted.AppendText("向日葵的花语是——太阳、光辉、高傲、忠诚、爱慕、沉默的爱。向日葵又叫望日莲，一个很美的名字");
  textRange1.CharacterFormat.TextColor = Color.Blue;
  textRange1.CharacterFormat.FontSize = 15;
  textRange1.CharacterFormat.UnderlineStyle = UnderlineStyle.Dash;
  document.SaveToFile("result.docx", FileFormat.Docx);


  //该部分为隐藏段落的代码
  Document doc = new Document();
  doc.LoadFromFile(@"C:\Users\Administrator\Desktop\雏菊.docx", FileFormat.Docx);
  Section sec = doc.Sections[0];
  Paragraph para = sec.Paragraphs[sec.Paragraphs.Count - 1];
  for (int i = 0; i < para.ChildObjects.Count;i++)
  {
  (para.ChildObjects[i] as TextRange).CharacterFormat.Hidden = true;

  }

  doc.SaveToFile("result1.docx", FileFormat.Docx);

 }
 }
}