Reflection , get all derived classes

Hello :

I have a nuget package , project. I have Implemented abstract class here.

Code Sample

//Nuget Package Project
namespace Common.Base
{
    public abstract class DocumentBase
    {

          public abstract byte[] Print(string Code, string Number);
    }
}

namespace Document.CraftFUN
{
    public class ProcessFUN : DocumentBase
    {
       
        public override byte[] Print(string Code, string Number)
        {
            byte[] ByteStream = null;

            PDFByteStream = GenerateCraft(Code, Number);

            return (ByteStream);
        }
    }
}
namespace Document.CraftGUM
{
    public class ProcessGUM : DocumentBase
    {
       
        public override byte[] Print(string Code, string Number)
        {
            byte[] ByteStream = null;

            PDFByteStream = GenerateCraft(Code, Number);

            return (ByteStream);
        }
    }
}


namespace Document.Iron
{
    public class ProcessIron : DocumentBase
    {
        throw new NotImplementedException("This isn't done yet");
    }
}

//Code in WEb API

//var cls = (DocumentBase)System.Reflection.Assembly.GetExecutingAssembly().CreateInstance(string className)
                if (Code.ToUpper() == "FUN")
                {
                    ProcessFUN pc = new ProcessFUN(_config);

                    foreach (string CraftToPrint in MyNumbers)
                    {
                        byte[] MemoBytes = pc.Print(Code.ToUpper(), CraftToPrint);
                    }
                 }
                  if (Code.ToUpper() == "GUM")
                {
                    ProcessGUM pc = new ProcessGUM(_config);

                    foreach (string CraftToPrint in MyNumbers)
                    {
                        byte[] MemoBytes = pc.Print(Code.ToUpper(), CraftToPrint);
                    }
                 }

Is there a better way of Handling the above code initialization using Reflection

//var cls = (DocumentBase)System.Reflection.Assembly.GetExecutingAssembly().CreateInstance(string className)

Thank you,

urpalshu