Thanks for sharing the details with me, @Scansy.
Let's isolate this unusual behaviour and get you back in working order. I recommend running your QuickBooks Desktop (QBDT) software as the Administrator. Once done, try to save and print the invoice.
Otherwise, if you already had and the result is still the same. There's a possibility that this issue is due to your company data file size. The performance of your QBDT software decreases as your company file increases. Thus, there's a delay in actions in printing and creating a PDF.
To sort this out, I got you this link that provides complete details on how to resolve QuickBooks Desktop performance issues: Manage your data file.
Also, I'm adding this useful article that can guide you in personalizing your sales form. This way, you can customize your invoice to show the details that is important to your business: Use and customize form templates.
Let me know if you need further assistance. I'll be around to help you anytime.
