Create PDF files in Xamarin

using GemBox.Pdf;
using System;
using System.ComponentModel;
using System.IO;
using System.Threading.Tasks;
using Xamarin.Essentials;
using Xamarin.Forms;

public partial class MainPage : ContentPage
{
    public MainPage()
    {
        ComponentInfo.SetLicense("FREE-LIMITED-KEY");
        InitializeComponent();
    }

    private string CreateDocument()
    {
        var document = new PdfDocument();

        for (int i = 0; i < pages.Value; ++i)
            document.Pages.Add();

        var filePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "Example.pdf");

        document.Save(filePath);

        return filePath;
    }

    private async void Button_Clicked(object sender, EventArgs e)
    {
        button.IsEnabled = false;
        activity.IsRunning = true;

        try
        {
            var filePath = await Task.Run(() => CreateDocument());
            await Launcher.OpenAsync(new OpenFileRequest(Path.GetFileName(filePath), new ReadOnlyFile(filePath)));
        }
        catch (Exception ex)
        {
            await DisplayAlert("Error", ex.Message, "Close");
        }

        activity.IsRunning = false;
        button.IsEnabled = true;
    }
}

Imports GemBox.Pdf
Imports System
Imports System.ComponentModel
Imports System.IO
Imports System.Threading.Tasks
Imports Xamarin.Essentials
Imports Xamarin.Forms

Partial Public Class MainPage
    Inherits ContentPage

    Public Sub New()
        ComponentInfo.SetLicense("FREE-LIMITED-KEY")
        InitializeComponent()
    End Sub

    Private Function CreateDocument() As String
        Dim document As New PdfDocument()

        For i As Integer = 0 To pages.Value - 1
            document.Pages.Add()
        Next

        Dim filePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "Example.pdf")

        document.Save(filePath)

        Return filePath
    End Function

    Private Async Sub Button_Clicked(sender As Object, e As EventArgs)
        button.IsEnabled = False
        activity.IsRunning = True

        Try
            Dim filePath = Await Task.Run(Function() CreateDocument())
            Await Launcher.OpenAsync(New OpenFileRequest(Path.GetFileName(filePath), New ReadOnlyFile(filePath)))
        Catch ex As Exception
            Await DisplayAlert("Error", ex.Message, "Close")
        End Try

        activity.IsRunning = False
        button.IsEnabled = True
    End Sub
End Class