You can use the DLL from net2.0 folder of the installation directory and it will work with all versions of .NET.
Unfortunately, I don't have the full Aspose software installed on my PC; The developer who originally used Aspose Total is long gone. I just have the old project that he created. In the project files, I found the "Aspose.Pdf.dll" and the "Aspose.Total.lic" files and have been able to use them to create my PDF report. The only problem is that the dll I have is for .Net 3.5 and I really need the .Net 4.0 version.
I see that there are a number of older versions of the software available on your web site, but my license only runs through 10/26/2012, and there aren't any downloads that old.
I was hoping that you might have an old version the installation files lying around...