How to open a PDF file at a specific zoom factor/percentage in C#, VB.NET

Sometimes, we may need to change the zoom factor when displaying a PDF file to fulfil our requirements. In this article, we will demonstrate how to open a PDF file at a specific zoom factor/percentage (such as default, 100 percent or any other zoom factors as required) by using Spire.PDF for .NET.

Now, please check the original zoom factor of the PDF file as below picture:

How to open a PDF file at a specific zoom factor/percentage in C#, VB.NET

Then refer to the following detail steps:

Step 1: Create a new instance of PdfDocument class, load the original PDF file and get its first page.

PdfDocument pdf = new PdfDocument("Stories.pdf");         
PdfPageBase page = pdf.Pages[0];

Step 2: Create a new PdfDestination object using the PdfDestination(PdfPageBase page, PointF location) class which has two parameters: the page and the page display location. Then set the value of its zoom property to the specific zoom factor/percentage.

PdfDestination dest = new PdfDestination(page, new PointF(-40f, -40f));
// Here we set its zoom factor to 100%. If you want to set the zoom factor to default, please set the value of zoom property to 0f.
dest.Zoom = 1f;

Step 3: Create a new instance of PdfGoToAction class and enable the zoom factor resetting action to be executed when the PDF file is opened.

PdfGoToAction gotoaction = new PdfGoToAction(dest);
pdf.AfterOpenAction = gotoaction;

Step 4: Save the PDF file.

pdf.SaveToFile("result.pdf");

The result zoom factor of the PDF file:

How to open a PDF file at a specific zoom factor/percentage in C#, VB.NET

Full codes:

[C#]
using Spire.Pdf;
using Spire.Pdf.Actions;
using Spire.Pdf.General;
using System.Drawing;

namespace Set_the_zoom_factor
{
    class Program
    {
        static void Main(string[] args)
        {
            PdfDocument pdf = new PdfDocument("Stories.pdf");         
            PdfPageBase page = pdf.Pages[0];
            PdfDestination dest = new PdfDestination(page, new PointF(-40f, -40f));
            dest.Zoom = 1f;
            PdfGoToAction gotoaction = new PdfGoToAction(dest);
            pdf.AfterOpenAction = gotoaction;
            pdf.SaveToFile("result.pdf");
        }
    }
}
[VB.NET]
Imports Spire.Pdf
Imports Spire.Pdf.Actions
Imports Spire.Pdf.General
Imports System.Drawing

Namespace Set_the_zoom_factor
	Class Program
		Private Shared Sub Main(args As String())
			Dim pdf As New PdfDocument("Stories.pdf")
			Dim page As PdfPageBase = pdf.Pages(0)
			Dim dest As New PdfDestination(page, New PointF(-40F, -40F))
			dest.Zoom = 1F
			Dim gotoaction As New PdfGoToAction(dest)
			pdf.AfterOpenAction = gotoaction
			pdf.SaveToFile("result.pdf")
		End Sub
	End Class
End Namespace