there is an option in whatsapp to email the chat to yourself .. save it .. and edit it so that you are printing 10 pages worth of chat only .. what i did was i printed it double sides 10 pages .. you can pick some of the important days in your life - 1st month anniversary .. bdays .. eid .. etc .. then pick few where you actually texted a lot .. so it shows a bit of a texting history as well ..
for the video/audio calls - take screenshots and add them to a word document - 9 or 12 to a page - make that another few pages ..
don't forget to print facebook status updates either .. when you got married or hit a milestone with each other ..
and yes, please, don't wait 4 months down the road to submit your papers .. gather everything ASAP and submit ASAP .. don't wait!
Good luck!