Learn English – Should there be a space before a percent sign

You have your choice. The white space goes either between paragraphs, or else in front of them, but probably not both.

Version 1, common on the Internet:

I am not fully sure if this is the right place for this question but I am guessing has something to do with structure and usage so hopefully it is alright here. Apologies if not.

I am getting confused when I write long reports and essays about when I should be writing paragraphs with a space separating and when I should have them following one another without a space.

I have been putting a space when it looks like too much of a wall of text but I am finding that paragraphs without spaces between them, look a bit weird.

Is it just when you start talking about something completely different that you should put a space, or should they follow on too? Should the space even be there or is it just something people do?

Version 2, common in print:

          I am not fully sure if this is the right place for this question but I am guessing has something to do with structure and usage so hopefully it is alright here. Apologies if not.
          I am getting confused when I write long reports and essays about when I should be writing paragraphs with a space separating and when I should have them following one another without a space.
          I have been putting a space when it looks like too much of a wall of text but I am finding that paragraphs without spaces between them, look a bit weird.
          Is it just when you start talking about something completely different that you should put a space, or should they follow on too? Should the space even be there or is it just something people do?

Both percent and per cent are acceptable. The ODO's AmE entry carries the following note:

Origin: mid 16th century: from per + cent, perhaps an abbreviation of pseudo-Latin per centum

Both spellings, percent and per cent, are acceptable, but consistency should be maintained. Percent is more common in US usage; per cent is more common in British usage.

The AmE vs. BrE difference can be confirmed (to an extent) by these two ngrams. Also, as you've stated, it's important to be consistent with whichever choice you make.