Need help on walkthrough submission process

I have been solving the retired machines, for each box I am trying to document various methods that I have learnt.

Can I just submit the walkthrough on machine page ? Does it have to be in a particular format ?

I would speculate to say;
Submit it via machine page, it asks for the URL where you will (should) be keeping your walk-through paper.

Format… PDF is probably the best regarding compression, that is just my opinion, can’t see what the requirement is but I have noticed most of them are in PDF format which should be a safe bet to go with.