InlineCollection Class

public sealed class InlineCollection : ElementCollection<Inline>

Public NotInheritable Class InlineCollection
	Inherits ElementCollection(Of Inline)

using System;
using System.IO;
using System.Linq;
using SautinSoft.Document;

namespace Example
{
    class Program
    {
        static void Main(string[] args)
        {
            // Get your free 100-day key here:   
            // https://sautinsoft.com/start-for-free/

            MergeParagraphs();
        }
        /// <summary>
        /// Merge all paragraphs into a single in an existing PDF document.
        /// </summary>
        /// <remarks>
        /// Details: https://sautinsoft.com/products/document/help/net/developer-guide/merge-paragraphs-in-pdf-document-net-csharp-vb.php
        /// </remarks>
        static void MergeParagraphs()
        {
            string inpFile = @"..\..\..\example.pdf";
            string outFile = @"Result.pdf";
            DocumentCore dc = DocumentCore.Load(inpFile);

            Paragraph firstPar = dc.GetChildElements(true, ElementType.Paragraph).First() as Paragraph;

            int lastIndex = firstPar.Inlines.Count;

            foreach (Paragraph par in dc.GetChildElements(true, ElementType.Paragraph).Reverse().Where(p => p != firstPar))
            {
                int last = lastIndex;
                foreach(Inline inline in par.Inlines)
                {
                    firstPar.Inlines.Insert(last++, inline.Clone(true));
                }
                par.Content.Delete();
            }

            dc.Save(outFile);
            System.Diagnostics.Process.Start(new System.Diagnostics.ProcessStartInfo(inpFile) { UseShellExecute = true });
            System.Diagnostics.Process.Start(new System.Diagnostics.ProcessStartInfo(outFile) { UseShellExecute = true });
        }
    }
}

Imports System
Imports System.IO
Imports System.Linq
Imports SautinSoft.Document

Namespace Example
    Friend Class Program
        Shared Sub Main(ByVal args() As String)
            MergeParagraphs()
        End Sub
        ''' Get your free 100-day key here:   
        ''' https://sautinsoft.com/start-for-free/
        ''' <summary>
        ''' Merge all paragraphs into a single in an existing PDF document.
        ''' </summary>
        ''' <remarks>
        ''' Details: https://sautinsoft.com/products/document/help/net/developer-guide/merge-paragraphs-in-pdf-document-net-csharp-vb.php
        ''' </remarks>
        Private Shared Sub MergeParagraphs()
            Dim inpFile As String = "..\..\..\example.pdf"
            Dim outFile As String = "Result.pdf"
            Dim dc As DocumentCore = DocumentCore.Load(inpFile)

            Dim firstPar As Paragraph = TryCast(dc.GetChildElements(True, ElementType.Paragraph).First(), Paragraph)

            Dim lastIndex As Integer = firstPar.Inlines.Count

            For Each par As Paragraph In dc.GetChildElements(True, ElementType.Paragraph).Reverse().Where(Function(p) p IsNot firstPar)
                Dim last As Integer = lastIndex
                For Each inline As Inline In par.Inlines
                    firstPar.Inlines.Insert(last, inline.Clone(True))
                    last += 1
                Next inline
                par.Content.Delete()
            Next par

            dc.Save(outFile)
            System.Diagnostics.Process.Start(New System.Diagnostics.ProcessStartInfo(inpFile) With {.UseShellExecute = True})
            System.Diagnostics.Process.Start(New System.Diagnostics.ProcessStartInfo(outFile) With {.UseShellExecute = True})
        End Sub
    End Class
End Namespace