The .NET Framework is required to run UltimatePDF. It is a free download from Microsoft. It can be downloaded from here. To see if you already have the framework loaded on your computer. Go to Add or Remove Programs in the control panel. It will be listed as Microsoft .NET Framework 1.1. The .NET framework system requirements are: 660 MB of hard disk space required, 190 MB additional hard disk space required for installation (850 MB total).