The problem is that the document above the signature is written by the user of the application. I have no control over its content; the last element could be a single-sentence paragraph, a long paragraph, a table, an image … Your solution would only be useful if I would encapsulate the last element of the document and the signature image within a single div and style it with page-break-inside:avoid. But I cannot do that because that would also prevent page breaks within the last, possibly long, paragraph of the document.