Check your Options on the Save As form and see if you have a sheet range specified by default under Sheet Options. If a range is set and it is beyond the actual number of sheets contained in the drawing, it will fail.
Ken Production: ST10 MP7, Testing: SE 2019 http://Grundey.blogspot.com
Check if in your Devices and Printers have a Solid Edge Velocity PS Printer 2.0, if don't have printer with this name, you will need to install Solid Edge Printer. Go to Solid Edge folder install, Program folder, search about PrinterInstaller.exe, with closed Solid Edge, execute that and them verify if printer is there and test if you can save pdf.
I remember that I have cleaned out all those printers... and removed also the Solid Edge Printer.. not realising that it was used to create the pdf files.. Will have a look in the morning.. and report back.. Thanks so far