Hello! I'm glad I'm not the only one still stressing about this project. 
Good to see others have done PDFs as well because I think that's what I read in the guidelines, but after checking out the chat it seems that lots of people are doing JPEGs. Also, I've just seen that they have a specific naming convention for the receipt screenshots and I have pretty much just shat a brick because I've only used the job ID and nothing else. Boo! Wonder if it's going to be a problem? I still have a few things to buy but I don't want to do anything until I get confirmation on how to format the bloody paperwork.
On a separate note, I got some payments through from mega old N*o jobs. That was a nice surprise. 