PDF/A-3 documents enable the transition from electronic paper to an electronic container that holds both human- and machine-readable versions of a document. An unlimited number of embedded documents for different processes can be included in a PDF/A-3 document. The e-invoice, which attaches a machine-readable XML document to the generated PDF invoice, is a very popular example.

The document processing libraries of TX Text Control make it easy to add and extract attachments from PDF/A-3 documents.

Preparing the Application

For the purposes of this demo, a .NET 6 console application will be created.

1. In Visual Studio, create a new Console App using .NET 6.

   

2. In the Solution Explorer, select your created project and choose Manage NuGet Packages... from the Project main menu.

   Select Text Control Offline Packages from the Package source drop-down.

   Install the latest versions of the following package:

   • TXTextControl.TextControl.ASP.SDK

   

Adding Attachments

The following code creates a new PDF document with a text document attached. The EmbeddedFile class represents the embedded file and can be added to the document using the EmbeddedFiles collection.

using System.Text;

using (TXTextControl.ServerTextControl tx = new TXTextControl.ServerTextControl()) {
   tx.Create();
   tx.Text = "This is a sample PDF document with an attachment";

   byte[] baAttachment = Encoding.ASCII.GetBytes("This is a textual attachment.");

   // create a new embedded file
   TXTextControl.EmbeddedFile efAttachment =
       new TXTextControl.EmbeddedFile("attachment.tx", baAttachment, null) {
          Description = "My embedded text file."
       };

   // add the embedded file to TextControl
   tx.DocumentSettings.EmbeddedFiles =
       new TXTextControl.EmbeddedFile[] { efAttachment };

   // save the document
   tx.Save("mypdf.pdf", TXTextControl.StreamType.AdobePDF);
}

When you open the document in Acrobat Reader, the attachment is listed in the Attachments sidebar.

Extracting Attachments

To extract attachments, the PDF must be loaded into TX Text Control using LoadSettings. The attachments are stored in the EmbeddedFiles array of attachments.

using (TXTextControl.ServerTextControl tx = new TXTextControl.ServerTextControl()) {
   tx.Create();

   TXTextControl.LoadSettings loadSettings = new TXTextControl.LoadSettings();

   tx.Load("mypdf.pdf", TXTextControl.StreamType.AdobePDF, loadSettings);

   foreach (TXTextControl.EmbeddedFile embeddedFile in loadSettings.EmbeddedFiles) {
      System.IO.File.WriteAllText(
         embeddedFile.FileName,
         Encoding.ASCII.GetString((byte[])embeddedFile.Data));
   }
}

TX Text Control provides comprehensive functionality for creating, manipulating, and analyzing PDF documents. To get started with TX Text Control, take a look at the Getting Started section.