Text starts a 1/3 down the page. Why? and how to Fix?

I use a Mac.  When printing out a large document containing both letter and legal size paper, my HP printer gives me the option of having the printer choose duh paper size based on the .pdf size.  The printer chooses the right paper size, however, on the second legal size paper and all subsequent legal size pages the text drops down about 3".  How do I fix this?