There are several solutions to your problem, all of them under "Multiple Page Printing Silverlight" on Google. I was having a similar problem and tried most of them. The only one that worked for me was this one:
http://www.codeproject.com/Tips/248553/Silverlight-converting-to-image-and-printing-an-UI
But honestly you should look at Google first and see whether there are better solutions to your specific problem.
Answering your question, there is a flag called HasMorePages that indicates you need a new page. Just type pe.HasMorePages and you will see.
Hope it helps