It works as himal977 mentioned.
Save the filled up form in A4. Go to the store and print in LEGAL size paper. Cut it to exact A4 size (29.7 cm X 21 cm) using their paper cutter.

if you don't know how to save filled up form in pdf, follow the link below:

http://collegeinfogeek.com/save-un-savable-data-entered-into-a-pdf-form/