Hi askmiraclesindia,
Once you're done preparing the invoice, go to Preview PDF. Choose print. Then under print settings --> More settings --> Paper size --> A5.
To make the content fit go to Scale --> Fit to page.
Hope this helps!
I have a similar problem.Having set the paper in QB the preview looked ok but the print was not.
Do i have to change the settings for the printer in Windows as well from A4?