Thanks ericaco! I got the app for my iPad.
One more question for you guys that have already uploaded. Warning: a stupid question: How did you name your files? The example they give has me confused. It says you can name something like "bank-statement-date-pdf" but you can't name it with a special character such as "bank.statement. date. pdf". I mean, isn't a dash a special character the same as a dot? I was going to just name stuff the obvious: Ex: Sundance passport or joint mail Apr 2018. Unless a space is considered a special character. Forgive me, but I am not super technical. This is why I am seriously considering having them scan and check this stuff. Yet, I really don't fancy rocking into London in the midst of Covid. Ugh.
If they suggest putting a dash, then only use dashes, because that is the format they want... no spaces, no other characters (generally, to read filenames, programming code doesn't like spaces, so dashes are used instead, and also a dot would indicate a change between file name and file format, so too many dots would cause the file to be read incorrectly in the system). It also looks like they don't want capital letters either.
So, just use the same format for every file (put a dash instead of a space in the filename, and there should always be a dot before pdf):
e.g.
applicant-passport.pdf
sponsor-passport.pdf
water-bill-april-2018.pdf
etc.