The note will be with the PDF file. If you have added note to a scanned page and exported the page as PDF file, a note icon will appear on the upper-right corner of the page. Tap the icon and you can view the note.

If you cannot view the note on your phone, it may because the PDF reader you are using does not support viewing notes. Please try to open the PDF file with other applications or sign into CamScanner web app at www.camscanner.com. In the web app, you can download the PDF file to view.