If you have saved the document at least once, and have any part of the document left visible, you can use the Revert > Browse all versions item in the File menu to restore any saved version.
If you have saved the document at least once since starting it and have Time Machine running, you should be able to enter Time Machine and scroll back to the most recent version prior to your deleting the page, and restore it from there.
If you do NOT have Time Machine (or some other back up system) running, it may still be possible to recover the document, the process could be quite involved, and quite expensive.
Barry