To add an additional page to the end of a note, go to the last page of your current note, and tap the ‘next’ arrow ( ) to the right of the page number.
To insert a page into a location other than the end of the note, open the page actions menu and choose Insert page. This will insert a page at the current position.
For details on how to insert a PDF, see How do I import a PDF?
For a video tutorial about inserting pages, see Squid - Working with Pages.