A few things to check
- Check if you have allowed page break inside tables in your Print Settings
- You may have to repeat table header on each page. Ref: Repeat Table Header in All Pages in DocType
- Once you have solved the table header issue, you will most likely face issue of content getting overlapped over the header on next page, view the following post for solving the issue
Repeat Item Table Header Overlap - #6 by Manan_Shah
Hope this helps.