Every pc builds its own list of paperkinds when printers are added and removed.
That’s why I cannot say which number is 30252 or 30256, however, oddly they are sometimes similar to those last 3 digits, but guess that’s coincidence. Its also likely that two users in the same room or otherwise could have different numbers for the same size ! Most rare for them to change for a single user, unless messing about with new forms or printers.
Here are a few from my Print to PDF today, but using paper=A4 or A5 is the max stability for CLI, those lower numbers 9 and 11 are fairly universal for most windows users around the globe, but its not guaranteed.
A4 (9) (11.69x8.27) (296.93x210.06)
A5 (11) (8.27x5.83) (210.06x148.08)
FOR the following I need to use paperkind=127 to print in the right column and 128 to print in the left column, but note although both of them are paper=A4 I cant use A4RH reliably but it does work sometimes with “paper=A4RH” (Note the different margins are stored in windows printer formats) For Japanese pages I need to use paperkind=12 or 13 but again with latest version “paper=B4 (JIS)” will often work whereas it did not before. Thus you could try -print-settings "paper=30256 Shipping"
B4 (JIS) (12) (14.33x10.12) (363.98x257.05)
B5 (JIS) (13) (10.12x7.17) (257.05x182.12)
A4RH (127) (11.69x8.27) (296.93x210.06)
A4LH (128) (11.69x8.27) (296.93x210.06)
Your common American sizes are also well fixed but SumatraPDF will default to “Letter” as the most acceptable locally. That is what will probably be applied unless forced otherwise, which is generally done via the print dialog.
Using PinterInformation you can ask for the list stored for the dymo printer and hope the names show as 30256 then look for paperkind (###) but that will only work with a recent pre-release copy of SumatraPDF built after that long GitHub discussion about how to make a change from book size pages.
so here is 127 output (the default would be large on the whole page)
sumatrapdf -print-to "Microsoft print to PDF" -print-settings "paperkind=127" Input.pdf
And if that was set to auto save without prompting as the currently viewed file in sumatraPDF I would instantly see this, To control the position to upper or lower I would need to add to windows those 2 different page layouts which would then have different numbers.