Welcome to the Community. I'm here to help get everything lined out for you today concerning the screen size in QuickBooks Desktop.
I've checked here and haven't found any changes happening on the screen size when saving a transaction as PDF. Let's start the troubleshooting by changing the QuickBooks DPI settings of the program.
Once done with the configuration, you can proceed with using the PDF Repair tool to fix the saving problem within QuickBooks Desktop. For the detailed steps on the process, please check out the article on this:
In case there's a need for you to reach out one of our Technical Support Specialists, I recommend bookmarking the article on how you can reach them:
As always, I'm here to help for any additional questions you may have about using QuickBooks Desktop. The Community is here to ensure your success.