Why can I not call a public method in my Web Part (User Control) from an Event Receiver?

I've added this Event Receiver (based on what I found here):

using System;
using System.Security.Permissions;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Security;
using Microsoft.SharePoint.Utilities;
using Microsoft.SharePoint.Workflow;

namespace PostTravelWizard.PostTravelItemEventReceiver
{
    /// <summary>
    /// List Item Events
    /// </summary>
    public class PostTravelItemEventReceiver : SPItemEventReceiver
    {
       /// <summary>
       /// An item was added.
       /// </summary>
       public override void ItemAdded(SPItemEventProperties properties)
       {
           base.ItemAdded(properties);
           //GeneratePDF(); <= "The name 'GeneratePDF' does not exist in the current context
       }

       /// <summary>
       /// The list received a context event.
       /// </summary>
       public override void ContextEvent(SPItemEventProperties properties)
       {
           base.ContextEvent(properties);
           // TODO: What "context event" occurs here? To what event should I respond?
       }

    }
}

I'm hoping to, when a List is updated (from the client side/Javascript), then retrieve those values in the code-behind to generate a PDF file. I have this code in my *.ascx.cs file:

public partial class PostTravelWizardWebPartUserControl : UserControl
{
    . . .

    public void GeneratePDF(PostTravelData ptd)
    {
        ;//bla
    }

...but it's not letting my call GeneratePDF() from the Event Receiver - it fails with

The name 'GeneratePDF' does not exist in the current context

Why? How can I rectify this asunto?

GeneratePDF is an instance method of PostTravelWizardWebPartUserControl class. In order to call it from PostTravelItemEventReceiver you have to create an instance of PostTravelWizardWebPartUserControl or let the method(GeneratePDF) be static.

Case 1

public override void ItemAdded(SPItemEventProperties properties)
{
    base.ItemAdded(properties);
    new PostTravelWizardWebPartUserControl().GeneratePDF();
}

Case 2

public partial class PostTravelWizardWebPartUserControl : UserControl
{
    public static void GeneratePDF(PostTravelData ptd)
    {
        ;//bla
    }
}


public class PostTravelItemEventReceiver : SPItemEventReceiver
{
    base.ItemAdded(properties);
    PostTravelWizardWebPartUserControl.GeneratePDF();
}