You can use the rand function to generate random text. To do this, move to a new paragraph and type =Rand(). You will get a collection of placeholder text. If you need more, you can determine the amount of text required by entering the number of paragraphs required in the parentheses, followed by a comma, and the number of sentences you would like in each paragraph.
So for example =rand(1,4) will give you one paragraph with four lines of text.