As recommended by @Lola, I reached out to the PDFForge support team. They stated this could not be done at this time. See quote below. Does anyone know if there is good third-party software out there that can accomplish what I am trying to do, or if there are past versions of PDFForge I could somehow install? Thank you.

Thank you for reaching out to PDF Forge Support. We’d like to inform you that, unlike the .NET Framework, .NET Core and .NET 5+ currently do not support generating a COM Type Library (TLB) directly from a .NET assembly.

That said, we understand how important this feature is for many of our users. Our development team is actively exploring possible solutions to bring back TLB generation in a way that aligns with the newer .NET platforms. While this may take some time, we’re committed to finding a path forward and will keep you updated on any progress.

We truly appreciate your patience and understanding in the meantime. If you have any further questions or need assistance with alternatives, please don’t hesitate to reach out.