split PDF into multiple files in C#

I met the same question, you can use itextsharp component tools to split the document

public Split(String[] args)
    {
        if (args.Length != 4) 
        {
            Console.Error.WriteLine("This tools needs 4 parameters:\njava Split srcfile destfile1 destfile2 pagenumber");
        }
        else 
        {
            try 
            {
                int pagenumber = int.Parse(args[3]);

                // we create a reader for a certain document
                PdfReader reader = new PdfReader(args[0]);
                // we retrieve the total number of pages
                int n = reader.NumberOfPages;
                Console.WriteLine("There are " + n + " pages in the original file.");

                if (pagenumber < 2 || pagenumber > n) 
                {
                    throw new DocumentException("You can't split this document at page " + pagenumber + "; there is no such page.");
                }

                // step 1: creation of a document-object
                Document document1 = new Document(reader.GetPageSizeWithRotation(1));
                Document document2 = new Document(reader.GetPageSizeWithRotation(pagenumber));
                // step 2: we create a writer that listens to the document
                PdfWriter writer1 = PdfWriter.GetInstance(document1, new FileStream(args[1], FileMode.Create));
                PdfWriter writer2 = PdfWriter.GetInstance(document2, new FileStream(args[2], FileMode.Create));
                // step 3: we open the document
                document1.Open();
                PdfContentByte cb1 = writer1.DirectContent;
                document2.Open();
                PdfContentByte cb2 = writer2.DirectContent;
                PdfImportedPage page;
                int rotation;
                int i = 0;
                // step 4: we add content
                while (i < pagenumber - 1) 
                {
                    i++;
                    document1.SetPageSize(reader.GetPageSizeWithRotation(i));
                    document1.NewPage();
                    page = writer1.GetImportedPage(reader, i);
                    rotation = reader.GetPageRotation(i);
                    if (rotation == 90 || rotation == 270) 
                    {
                        cb1.AddTemplate(page, 0, -1f, 1f, 0, 0, reader.GetPageSizeWithRotation(i).Height);
                    }
                    else 
                    {
                        cb1.AddTemplate(page, 1f, 0, 0, 1f, 0, 0);
                    }
                }
                while (i < n) 
                {
                    i++;
                    document2.SetPageSize(reader.GetPageSizeWithRotation(i));
                    document2.NewPage();
                    page = writer2.GetImportedPage(reader, i);
                    rotation = reader.GetPageRotation(i);
                    if (rotation == 90 || rotation == 270) 
                    {
                        cb2.AddTemplate(page, 0, -1f, 1f, 0, 0, reader.GetPageSizeWithRotation(i).Height);
                    }
                    else 
                    {
                        cb2.AddTemplate(page, 1f, 0, 0, 1f, 0, 0);
                    }
                    Console.WriteLine("Processed page " + i);
                }
                // step 5: we close the document
                document1.Close();
                document2.Close();
            }
            catch(Exception e) 
            {
                Console.Error.WriteLine(e.Message);
                Console.Error.WriteLine(e.StackTrace);
            }
        }

    }

You can use a PDF library like PDFSharp, read the file, iterate through each of the pages, add them to a new PDF document and save them on the filesystem. You can then also delete or keep the original.

It's quite a bit of code, but very simple and these samples should get you started.

http://www.pdfsharp.net/wiki/Default.aspx?Page=ConcatenateDocuments-sample&NS=&AspxAutoDetectCookieSupport=1

A previous question answers your partially - how to split pdf documents, if you know where the barcodes are then you can split the documents easily:

How can I split up a PDF file into pages (preferably C#)

The recommendation is a library called PDFSharp and a sample demonstrating PDF splitting.