You can add a line break to generated content by inserting the character sequence "\A", e.g.:

content: "this is the first line\Aand this is the second one.";

In XML documents the setting of the whitespace property to "pre", "pre-wrap" or "pre-line" in a style section of the document or in a CSS stylesheet is required for the recognition of the character sequence "\A", e.g.:

@page {
@top-center {
white-space: pre;
content: "this is the first line\Aand this is the second one."
}
}

For HTML documents this is not necessary as it is done in the HTML default stylesheet.