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Technical Article

Working with PDF Attachments in Delphi using PDFium Component

· PDF Programming

PDF documents can contain embedded file attachments—a powerful feature for bundling related files like spreadsheets, images, or supporting documents. The Attachment demo shows how to work with PDF attachments using PDFium VCL.

Overview

This demo provides complete attachment management including listing, extracting, adding, and deleting file attachments from PDF documents. It’s essential for document management systems that need to handle complex PDF files.

Key Features

  • List Attachments – View all embedded files in a PDF
  • Extract Attachments – Save attachments to disk
  • Add Attachments – Embed new files into PDFs
  • Delete Attachments – Remove attachments from PDFs
  • View Details – See attachment names and sizes

PDFium DLL Requirements

Before running any PDFium VCL application, ensure the PDFium DLL files are installed:

  • pdfium32.dll / pdfium64.dll – Standard versions (~5-6 MB)
  • pdfium32v8.dll / pdfium64v8.dll – With V8 JavaScript engine (~23-27 MB)

Installation: Run PDFiumVCL\DLLs\CopyDlls.bat as Administrator to automatically copy the DLLs to Windows system directories.

Listing Attachments

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procedure TFormMain.RefreshAttachmentList;
var
  I: Integer;
  AttachmentName: string;
  AttachmentData: TBytes;
  SizeStr: string;
begin
  ListBoxAttachments.Items.Clear;
  
  if not Pdf.Active then
    Exit;
    
  for I := 0 to Pdf.AttachmentCount - 1 do
  begin
    AttachmentName := Pdf.AttachmentName[I];
    AttachmentData := Pdf.Attachment[I];
    
    // Format size
    if Length(AttachmentData) >= 1024 * 1024 then
      SizeStr := Format('%.2f MB', [Length(AttachmentData) / (1024 * 1024)])
    else if Length(AttachmentData) >= 1024 then
      SizeStr := Format('%.2f KB', [Length(AttachmentData) / 1024])
    else
      SizeStr := Format('%d bytes', [Length(AttachmentData)]);
      
    ListBoxAttachments.Items.Add(Format('%s (%s)', [AttachmentName, SizeStr]));
  end;
  
  LogStatus(Format('Found %d attachment(s)', [Pdf.AttachmentCount]));
end;

Extracting Attachments

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procedure TFormMain.ButtonExtractAttachmentClick(Sender: TObject);
var
  Index: Integer;
  AttachmentName: string;
  AttachmentData: TBytes;
  FileStream: TFileStream;
begin
  Index := GetSelectedAttachmentIndex;
  if Index < 0 then
  begin
    LogStatus('Please select an attachment to extract.');
    Exit;
  end;
  
  try
    AttachmentName := Pdf.AttachmentName[Index];
    AttachmentData := Pdf.Attachment[Index];
    
    SaveDialog.FileName := AttachmentName;
    if SaveDialog.Execute then
    begin
      FileStream := TFileStream.Create(SaveDialog.FileName, fmCreate);
      try
        if Length(AttachmentData) > 0 then
          FileStream.WriteBuffer(AttachmentData[0], Length(AttachmentData));
          
        LogStatus('Extracted: ' + SaveDialog.FileName);
      finally
        FileStream.Free;
      end;
    end;
    
  except
    on E: Exception do
      LogStatus('Error extracting attachment: ' + E.Message);
  end;
end;

Adding Attachments

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procedure TFormMain.ButtonAddAttachmentClick(Sender: TObject);
var
  AttachmentName: string;
  FileData: TBytes;
  FileStream: TFileStream;
begin
  if not Pdf.Active then
  begin
    LogStatus('Please load or create a PDF document first.');
    Exit;
  end;
  
  OpenDialog.Filter := 'All Files|*.*';
  if OpenDialog.Execute then
  begin
    try
      // Read file into byte array
      FileStream := TFileStream.Create(OpenDialog.FileName, fmOpenRead);
      try
        SetLength(FileData, FileStream.Size);
        if FileStream.Size > 0 then
          FileStream.ReadBuffer(FileData[0], FileStream.Size);
      finally
        FileStream.Free;
      end;
      
      // Use filename as attachment name
      AttachmentName := ExtractFileName(OpenDialog.FileName);
      
      // Create attachment slot
      if Pdf.CreateAttachment(AttachmentName) then
      begin
        // Find the new attachment and set its data
        Pdf.Attachment[Pdf.AttachmentCount - 1] := FileData;
        
        LogStatus('Added attachment: ' + AttachmentName);
        RefreshAttachmentList;
      end
      else
        LogStatus('Failed to create attachment: ' + AttachmentName);
        
    except
      on E: Exception do
        LogStatus('Error adding attachment: ' + E.Message);
    end;
  end;
end;

Deleting Attachments

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procedure TFormMain.ButtonDeleteAttachmentClick(Sender: TObject);
var
  Index: Integer;
  AttachmentName: string;
begin
  Index := GetSelectedAttachmentIndex;
  if Index < 0 then
  begin
    LogStatus('Please select an attachment to delete.');
    Exit;
  end;
  
  try
    AttachmentName := Pdf.AttachmentName[Index];
    
    if MessageDlg(Format('Delete attachment "%s"?', [AttachmentName]),
      mtConfirmation, [mbYes, mbNo], 0) = mrYes then
    begin
      if Pdf.DeleteAttachment(Index) then
      begin
        LogStatus('Deleted attachment: ' + AttachmentName);
        RefreshAttachmentList;
      end
      else
        LogStatus('Failed to delete attachment.');
    end;
    
  except
    on E: Exception do
      LogStatus('Error deleting attachment: ' + E.Message);
  end;
end;

Accessing Attachment Properties

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// Number of attachments
Count := Pdf.AttachmentCount;
 
// Attachment name at index
Name := Pdf.AttachmentName[Index];
 
// Attachment data as byte array
Data := Pdf.Attachment[Index];
 
// Set attachment data
Pdf.Attachment[Index] := NewData;
 
// Create new attachment
Success := Pdf.CreateAttachment('filename.txt');
 
// Delete attachment
Success := Pdf.DeleteAttachment(Index);

Creating a New Document with Attachments

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procedure CreatePdfWithAttachments;
var
  Pdf: TPdf;
  FileData: TBytes;
  FileStream: TFileStream;
begin
  Pdf := TPdf.Create(nil);
  try
    // Create new document
    Pdf.CreateDocument;
    Pdf.Active := True;
    
    // Add a page
    Pdf.AddPage(1, 595, 842);
    Pdf.PageNumber := 1;
    Pdf.AddText('Document with Attachments', 'Arial', 18, 50, 750,
      clBlack, $FF, 0.0);
    
    // Add first attachment
    FileStream := TFileStream.Create('data.csv', fmOpenRead);
    try
      SetLength(FileData, FileStream.Size);
      FileStream.ReadBuffer(FileData[0], FileStream.Size);
    finally
      FileStream.Free;
    end;
    
    if Pdf.CreateAttachment('data.csv') then
      Pdf.Attachment[0] := FileData;
      
    // Add second attachment
    FileStream := TFileStream.Create('readme.txt', fmOpenRead);
    try
      SetLength(FileData, FileStream.Size);
      FileStream.ReadBuffer(FileData[0], FileStream.Size);
    finally
      FileStream.Free;
    end;
    
    if Pdf.CreateAttachment('readme.txt') then
      Pdf.Attachment[1] := FileData;
      
    // Save
    Pdf.SaveAs('document_with_attachments.pdf');
    
  finally
    Pdf.Active := False;
    Pdf.Free;
  end;
end;

Saving Document After Modifications

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procedure TFormMain.ButtonSaveDocumentClick(Sender: TObject);
var
  CurrentFileName, TempFileName: string;
  WasActive: Boolean;
begin
  SaveDialog.Filter := 'PDF Files|*.pdf|All Files|*.*';
  SaveDialog.DefaultExt := 'pdf';
  
  if SaveDialog.Execute then
  begin
    try
      CurrentFileName := Pdf.FileName;
      WasActive := Pdf.Active;
      
      // If saving to the same file, use temporary file
      if WasActive and SameText(CurrentFileName, SaveDialog.FileName) then
      begin
        TempFileName := SaveDialog.FileName + '.tmp';
        
        if Pdf.SaveAs(TempFileName) then
        begin
          // Close, delete old, rename new
          Pdf.Active := False;
          
          if DeleteFile(CurrentFileName) then
          begin
            if RenameFile(TempFileName, SaveDialog.FileName) then
            begin
              // Reload
              Pdf.FileName := SaveDialog.FileName;
              Pdf.Active := True;
              LogStatus('Document saved successfully.');
            end;
          end;
        end;
      end
      else
      begin
        // Save to different file
        if Pdf.SaveAs(SaveDialog.FileName) then
          LogStatus('Document saved: ' + ExtractFileName(SaveDialog.FileName))
        else
          LogStatus('Failed to save document.');
      end;
      
    except
      on E: Exception do
        LogStatus('Error saving document: ' + E.Message);
    end;
  end;
end;

Displaying Attachment Details

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procedure TFormMain.ListBoxAttachmentsClick(Sender: TObject);
var
  Index: Integer;
  AttachmentName: string;
  AttachmentData: TBytes;
begin
  Index := GetSelectedAttachmentIndex;
  
  if Index >= 0 then
  begin
    AttachmentName := Pdf.AttachmentName[Index];
    AttachmentData := Pdf.Attachment[Index];
    
    MemoDetails.Lines.Clear;
    MemoDetails.Lines.Add('Name: ' + AttachmentName);
    MemoDetails.Lines.Add('Size: ' + IntToStr(Length(AttachmentData)) + ' bytes');
    MemoDetails.Lines.Add('Index: ' + IntToStr(Index));
    
    // Try to detect file type from extension
    if EndsText('.txt', AttachmentName) or
       EndsText('.csv', AttachmentName) then
      MemoDetails.Lines.Add('Type: Text file')
    else if EndsText('.pdf', AttachmentName) then
      MemoDetails.Lines.Add('Type: PDF document')
    else if EndsText('.jpg', AttachmentName) or
            EndsText('.png', AttachmentName) then
      MemoDetails.Lines.Add('Type: Image file')
    else
      MemoDetails.Lines.Add('Type: Binary file');
  end;
end;

Use Cases

  • Document Packages – Bundle main document with supporting files
  • Form Submissions – Attach evidence or supporting documents to forms
  • Technical Manuals – Include CAD files, spreadsheets, or source code
  • Legal Documents – Attach exhibits and appendices
  • Archive Management – Extract attachments for processing

Conclusion

The Attachment demo shows how PDFium VCL provides complete control over PDF file attachments. Whether you’re building a document management system or processing PDF forms with embedded files, these APIs make it straightforward.

The ability to add, extract, and delete attachments programmatically opens up many possibilities for document automation and processing workflows.

Manage PDF attachments with ease using Delphi PDFium VCL.