PDF attachments allow users to see more details on a particular point by visiting attachments inside the PDF. Basically, there are two types of attachments in PDF: document level attachment and annotation attachment. Below are the differences between them.
- Document Level Attachment (represented by PdfAttachment class): A file attached to a PDF at the document level won't appear on a page, but only appear in the PDF reader's "Attachments" panel.
- Annotation Attachment (represented by PdfAttachmentAnnotation class): A file that is attached to a specific position of a page. Annotation attachments are shown as a paper clip icon on the page; reviewers can double-click the icon to open the file.
In this article, you will learn how to extract these two kinds of attachments from a PDF document in C# and VB.NET using Spire.PDF for .NET.
Install Spire.PDF for .NET
To begin with, you need to add the DLL files included in the Spire.PDF for.NET package as references in your .NET project. The DLL files can be either downloaded from this link or installed via NuGet.
PM> Install-Package Spire.PDF
Extract Attachments from PDF in C# and VB.NET
The document level attachments of a PDF document can be obtained through PdfDocument.Attachments property. The following steps illustrate how to extract all document level attachments from a PDF document and save them to a local folder.
- Create a PdfDocument object.
- Load a PDF file using PdfDocument.LoadFromFile() method.
- Get the attachment collection from the document through PdfDocument.Attachments property.
- Get the data of a specific attachment through PdfAttachment.Data property.
- Write the data to a file and save to a specified folder.
- C#
- VB.NET
using Spire.Pdf;
using Spire.Pdf.Attachments;
using System.Net.Mail;
namespace ExtractAttachments
{
class Program
{
static void Main(string[] args)
{
//Create a PdfDocument object
PdfDocument doc = new PdfDocument();
//Load a PDF file that contains attachments
doc.LoadFromFile("C:\\Users\\Administrator\\Desktop\\Attachments.pdf");
//Get the attachment collection of the PDF document
PdfAttachmentCollection attachments = doc.Attachments;
//Specific output folder path
string outputFolder = "C:\\Users\\Administrator\\Desktop\\output\\";
//Loop through the collection
for (int i = 0; i < attachments.Count; i++)
{
//Write attachment to a file
File.WriteAllBytes(outputFolder + attachments[i].FileName, attachments[i].Data);
}
}
}
}
Extract Annotation Attachments from PDF in C# and VB.NET
Annotation attachment is a page-based element. To get annotations from a specific page, use PdfPageBase.AnnotationsWidget property. After that, you’ll need to determine if a specific annotation is an annotation attachment. The follows are the steps to extract annotation attachments from a PDF document and save them to a local folder.
- Create a PdfDocument object.
- Load a PDF file using PdfDocument.LoadFromFile() method.
- Get a specific page from the document through PdfDocument.Pages[] property.
- Get the annotation collection from the page through PdfPageBase.AnnotationsWidget property.
- Determine if a specific annotation is an instance of PdfAttachmentAnnotationWidget. If yes, write the annotation attachment to a file and save it to a specified folder.
- C#
- VB.NET
using Spire.Pdf;
using Spire.Pdf.Annotations;
namespace ExtractAnnotationAttachments
{
class Program
{
static void Main(string[] args)
{
//Create a PdfDocument object
PdfDocument doc = new PdfDocument();
//Load a PDF file that contains attachments
doc.LoadFromFile("C:\\Users\\Administrator\\Desktop\\AnnotationAttachments.pdf");
//Specific output folder path
string outputFolder = "C:\\Users\\Administrator\\Desktop\\Output\\";
//Loop through the pages
for (int i = 0; i < doc.Pages.Count; i++)
{
//Get the annotation collection
PdfAnnotationCollection collection = doc.Pages[i].AnnotationsWidget;
//Loop through the annotations
for (int j = 0; j < collection.Count; j++)
{
//Determine if an annotation is an instance of PdfAttachmentAnnotationWidget
if (collection[j] is PdfAttachmentAnnotationWidget)
{
//Write annotation attachment to a file
PdfAttachmentAnnotationWidget attachmentAnnotation = (PdfAttachmentAnnotationWidget)collection[j];
String fileName = Path.GetFileName(attachmentAnnotation.FileName);
File.WriteAllBytes(outputFolder + fileName, attachmentAnnotation.Data);
}
}
}
}
}
}
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