To print PDF file with the notes contents to be displayed in printout too, you have to click the button "Summarize Comments "in Foxit PDF Editor/Reader print dialog box, then our Foxit PDF Editor/Reader prints the summarized comments(including the note contents) as well while printing the document.
If you want to print the text in the Notes and Pop-ups in the original position and don't want to print the summarized comments at the end of the PDF document, you could go to File > Preferences > Commenting > check Print notes and pop-ups then perform the printing.
Note: The Print notes and pop-ups is supported since version 9.2.0.