PDF document thumbnails, appearing in the left-hand corner of a PDF reader, provide miniature previews of document pages. The 'Thumbnail View' pane allows you to view page thumbnails of all the pages included in the PDF document and you can simply click on the thumbnail to quickly travel to that page.

This article presents how to create a PDF document thumbnail view in your own .NET PDF viewer via Spire.PDFViewer. Detailed steps are as below:

Step 1: Create a new project in Windows Forms Application.

Step 2: Add Spire.PDFViewer control to VS Toolbox.

Step 3: Design Form1.

• Add a ToolStrip to Form1. Insert two Buttons, one TextBox and one Label to ToolStrip.
• Drag PdfDocumentThumbnail and PdfDocumentViewer control from Toolbox to Form1.
• Set properties of the Buttons, Labels, TextBox, PdfDocumentThumbnail and PdfDocumentViewer as below.

Step 4: Set code for btnOpen and btnThumbnailRatio.

1) Create a OpenFileDailog in btnOpen click event which enables you to open a file with correct type.

    private void btnOpen_Click(object sender, EventArgs e)
 {
     OpenFileDialog dialog = new OpenFileDialog();
     dialog.Filter = "PDF document(*.pdf)|*.pdf";
     DialogResult result = dialog.ShowDialog();
     if (result == DialogResult.OK)
     {
         string pdfDocument = dialog.FileName;
         this.pdfDocumentViewer1.LoadFromFile(pdfDocument);
     }

 }

2) Set zoom ratio for thumbnail view mode.

  private void btnThumbnailRatio_Click(object sender, EventArgs e)
  {
      if (this.pdfDocumentViewer1.IsDocumentLoaded)
     {
          int percent = 0;
          bool isNumeric = int.TryParse(this.txtThumbnailRatio.Text, out percent);
          if (isNumeric)
          {
              this.pdfDocumentThumbnail1.ZoomPercent =Math.Abs(percent);
          }
      }
  }

Run this program and open an existing PDF document, you'll get following output: