If the last line of a paragraph is also the first line of a page it is called a widow.
If the first line of a paragraph is also the last line of a page it is called an orphan.
PDFreactor by default avoids widows and orphans by adding a page break before the paragraph. This behaviour can be changed by the CSS properties 'widows' and 'orphans'. The default values are:
@page {
orphans: 2;
widows: 2;
}Changing the value to 1 will allow widows and orphans. Changing it to higher integer values will prevent even multiple line widows and orphans. (e.g.: 'orphans: 5' means that if the first 4 lines of a paragraph are the last 4 lines of a page these lines are considered an orphan.)