PIAPS_CW/WinFormsApp/FormPreviewPDF.cs

using Spire.Pdf;
using Spire.Pdf.Graphics;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WinFormsApp
{
    public partial class FormPreviewPDF : Form
    {
        public string src { get; set; }
        public FormPreviewPDF()
        {
            InitializeComponent();
        }

        private void buttonPrint_Click(object sender, EventArgs e)
        {
            DialogResult = DialogResult.OK;
            Close();
        }

        private void FormPreviewPDF_Load(object sender, EventArgs e)
        {
            var doc = new PdfDocument();
            doc.LoadFromFile(src);
            Image image = doc.SaveAsImage(0, PdfImageType.Bitmap, 500, 1000);
            pictureBox.Image = image;
            pictureBox.SizeMode = PictureBoxSizeMode.Zoom;
        }

        private void buttonCancel_Click(object sender, EventArgs e)
        {
            DialogResult = DialogResult.Cancel;
            Close();
        }
    }
}