Set the page size or go to custom mode and set the height and width of the page as you needed (take the measurement from the standard scale and note those values in inches and enter them in the desired box)
you can set the page size through the vba code, see the "active document" class for more information.
If you created that form in MS-WORD, that has nothing to do with opened WORD document then follow POINT#1, the printer functionality (paper size and quality) works with the active printer you have set in the printer control panel. CUSTOM mode comes with your printer and provided driver (not all printers have this mode).
I came across such situation when needed to print a sale bill of medical transaction, where the bill layout is 1/3 of the paper. I have to take care of the situation through the VB
code (Visual Basic 6.0). So here ways are different but approach is same.
Hope this helps.