How do I get this light grey background?

Xxxx this libreoffice writer is not user-friendly. How do I get this light grey background?
Lightgreybackground

Sorry if this has already been discussed somewhere else, but I honestly can’t be bothered to find it in this mess.

No need to be rude; behave yourself.
To get any help, give minimum technical information: OS name, LO version and save format.
Unless you requested it through style definition (either paragraph or character styles), this light gray background is a clue that some data has been generated, not typed by user. This can be the result of cross-referencing or more generally something inserted through fields.
Unfortunately your screenshot is useless because you didn’t enable View>Formatting Marks.

Please, improve your question by editing it (don’t use a comment to answer) and attach your file.

2 Likes

I’m not attaching the file, it contains a lot of personal information

Then make a copy, reduce to 1 page, remove personal information, make sure the problem persists and attach the reduced version.